How to test an igniter on a Toyota/Lexus

How to test an igniter on a Toyota/Lexus

what I want to do is walk you through one we have a vehicle it’s a 91 Lexus ls400 and we’re going to show and illustrate how to determine if it’s a pull-up or pulldown type circuit how to manipulate the signal and make the ignitor receive the signal from the computer and fire the coil this is going to aid in no spark diagnosis in particular when you’re not sure if the coil is bad the igniter is bad and computers bad wiring is bad or maybe you have an input problem this is going to make that so much faster so we want to focus on our IDT signal how do we know it was the IGT signal we got a little bit of help with that so let’s come down and take a look at that real quick and on this we pulled this out of Mitchell it was a description of circuit design we need a little bit of help and I highlighted in yellow it says primary circuit is turned off when the ECU that’s electronic control unit that’s an old terminology for PCM today’s cars when the ECU sends a signal to the igniter on the IDT wire so here’s what we got I wrote this down it’s an electronic type switch input I’ll call this module to module communication and our EGR IDT signal is the ECU to igniter control signal the ECU generates the signal based on the cam crank sensor input sends a square wave to the IG to our sorry to the igniter on the IGT circuit what we don’t know right now because we want to do a bypass test is it a pull out for pulldown circuit and can we identify a circuit design alright so looking at the wiring diagram looking at our IDT wire we’re going to see if this diagram is able to tell us circuit design is it pull up is it pull down so map the IDT circuit this is what you would do if you’re working on the collar and right there says i gt1 so basically what we have is an ECU and we have an igniter and that’s it so the answer is no you cannot identify circuit design on a wiring diagram it is not possible on an electronic design so you have to do it another way what we’re going to do while we’re here is map out the other one because we’re going to do the both on the car we’ll map out the other igt on the other igniter and it’s pin 2 and it’s also going to go to the computer and there’s my IG t2 signal so what we’re going to try to determine circuit design on the car using a voltmeter what we want to know are the igniter sending voltage to the ECU and the ECU’s pulling it to ground making the square wave or is the ECU generating the square wave sending it to the igniter in a pull-up fashion so what we’re going to do when we come down to the igniter down here we’ll take a measurement depending on if our voltage is high let’s say it’s 12 volts we’ll take a test light to ground and we’ll touch it on the wire and we’ll pull the circuit down and it’s going to spark it will react if the voltage is low on that wire say zero volts we’ll take our test light to power and touch it on and off and we’ll make it react so if it’s zero volts I would call that a pull-up design circuit if it’s 12 volts I’ll call out a pulldown design circuit we need to know this to be able to do this kind of test all right we’re going to go to the car okay we’re under the hood I have the two IDT wires t pin one for each igniter this is a definitely a goofy system has two different distributors two different coils and we have two different igniters that control those two from coils and so we’re going to do the ignitor bypass test or ECU bypass test and see if these igniters function and what we need to do first is we need to determine if we need to give this t pin the signals a a power or a ground is it pull-up or pulldown measure the voltage with a voltmeter key is on T pin on that connector I got zero volts on that wire and I have zero volts on that wire and so what I know is these two igniters need to have a high low signal on-off signal to be able to turn the transistor on and off the fire the coils and I know now that I need to give these two guys high voltage not low voltage I’m not going to ground them I’m going to give them power I’m going to do it through my test light this is going to reduce the current flow in the circuit any ahh overload of current or if I would touch the wrong wire my test light would just light I’m not going to hurt anything test lights connected to battery positive when I touch my test light to ground it should light that’s important part of the step come down here this odd right igniter is going to fire the coil on that side and this left igniter is going to fire the coil on this side I already have the coil wire unplugged from the distributor and it’s laying on the valve cover over here near it same thing on this side a little bit longer air gap here watch when I touch this t pin for this side with my test light connected the battery positive simulating the ECU’s on/off square wave touch that wire on/off I should get a spark every time same thing with the other igniter on this side touch this on and off and you see I’m getting a spark every time I do it something to note my test light if you watch it is not lighting when I touch these pins right this is just a control signal it’s a low voltage circuit it doesn’t carry any current flow I’m just using my test light to manipulate the sir and pull it up it’s a pull up design circuit to make these igniters fire what’s nice about this test and what we just did if the car comes in and it’s a no spark situation no guesswork involved no reason to try a coil no reason to try and igniter igniters find coils fine the wiring is fine for the igniter and coils the direction would be cam crank input the direction would be going toward the inputs which would be the kamek crank sensor or going toward the ECU as a problem if this car came in as a no spark that’s how you do a bypass using section two of my book pull up pull down circuitry

About the Author: Michael Flood


  1. Hi Paul, can the ignitor module itself cause a misfire randomly over a long period of time? or most likely be a crank sensor or pcm problem? I had an ignitor die pretty quick,I hear the dizzy shaft if there's play can upset crank signal, crank sensors in the dizzy on my car. Got this misfire issue, swapped back ignitor but still a random misfire, have replaced all ignition parts so next I've got a fuel gauge on the way to check the regulator and pump as the filter is new too.

  2. Nice to know. The circuit design does indicate what is going on. The trained mind will know the untrained mind will never know but it is nice to see someone tell us all how to do it one way or the other.

  3. Hi Paul

    I have a customer with a SC400 Lexus with the same engine as the vehicle you are working on, it has injector pulse but no spark, I have checked the IGT & IGF with my pico and I have both of them on both ignitors, my question is if the IGT & IGF are both present is it still possible that the CAS has failed or can it only be both ignitors failed???

  4. Your focus is certainly toward the ignitors but for both of them to fail at the same time seems unlikely. Make sure you check the main power and ground to the ignitors and also make sure the coil(-) wire (measured at the ignitors) is reading a steady battery voltage during cranking. In a working system this coil(-) wire should be pulsing. If you have my eBook refer to Section 22 page 8 and 9 for "control" testing of coil (-)

  5. Hi Paul
    Thanks for your help, I agree that both ignitors prob have not failed, I have noticed there is no ground at the ignitor connectors, do they use the ignitor body for a ground?????, I have checked power supply and they are both good while cranking??

  6. ok cool. do the control testing with a test light flow chart and let me know what you find. also watch my subaru video where i am demonstrating this procedure

  7. i gotta get that ebook !… its great to see you using DMM .. would be cool if you showed how to do more test on other sensors with a DMM.. but i bet there something about that in the book too ..

  8. you will not be disappointed if you do. and i do have dmm testing where applicable all through the ebook. fill out your name and email on my webpage and I will send you more info. about it.

  9. nice! thank you!
    i think i had this one in section 2 on pull-up design circuits right?
    or maybe an example of module to module communication.
    there are so many that fall in multiple subjects it's getting hard to remember where i placed them

  10. Paul, I need ur help. I have ford f150 truck with waste spark, it has 3 wire. One is power 12v always, rest of 2 wire are control wire for 2 ignition coil firing total of 4 spark plug, 2 per coil. problem is iam not getting pulsed ground in those 2 wires. pls note PCM has built in ICM . I have to check crank sensor and cam sensor, but after watching ur vides, as part of curiosity, I connected test light grounded and touched momentarily the control wire and see no spark in plug.. any advise.

  11. continuation.. when I connected my grounded test light to control wire it was lighting.. not sue whether it should light or not light. my goal is to tap the control wire with grounded test light on and off to create pulse.. if test light light I am not sure what this means..

  12. that test will not work for an ignition coil primary circuit. Coils draw from 6-10 amps of current each and your test light doesn't support that type of flow.
    Does it have no spark on either coil pack or just one?

  13. Thanks Paul for reply. it doesn't have spark on either coil pack. I am sure the issue is not coil pack just want to experiment ur video for primary circuit. issue is no pulse. I am thinking of using a jumper wire or power probe to test primary circuit.. will wait for ur advise.. will bad Cam shaft sensor will stop the spark , i tested crankshaft i see good wave form, i got injection pulse. will bad CAM shaft stop the spark? thanks in advance.

  14. Hi Paul in this video, u had made a point twice, (test light should not light up) when u connect ur positive powered test light to grounded igniter to create a pulse. I am not sure what it means if test light lid, when u are pulling up the circuit.

  15. Paul, I tried today and it worked, what I did is like used power hook (newly introduced by power probe) and it have the ability to set max amp. I set to 5 and can be extended to 30 amp.. you might like this tool, because it can pulse AC signal, with very less current 50 milliamps as well.. it have lot of features just an fyi..

  16. Ok I actually have the same car having that problem and you help me out a long way with your video so I was wondering what could I check next because I tried that and had no spark so plz if you can help me out I will appreciate it brother

  17. Ok I went out there with my laptop and tried to do what I saw you do but I don't know which wires on either side to put the metal prongs in so if you have no problem tellin me then I could stratch it off list

  18. Just backprobe the igniter with it plugged in and with the key on. One of the wires should be hot and another should be a constant ground (unless the ground is on the igniter housing)

  19. Scanner I did the test and got input voltage of 5 but the coils are not firing at all so is that a bad igniter because I did trace the wires from each coil on both sides to make sure that the wires are good so I'm really trying help brother

  20. So I found I have a pull up design on my 4runner. I took a test light from bat positive to my igt wire and got spark every time. So I went and checked my cam and crank coils located inside distributor and found that my g- and NE weren't within specification. I also saw that the air gap on one of the coils were arching as the distributor turned. Could this be the cause of my "start" "nostart" problem I'm having?? And am I going to need a new distributor?

  21. what a huge time-saver! 

    apparently this is the foremost automotive wizard in America – Eric the car-guy is bush-league compared to Paul "Scanner" Danner  #mindblown

  22. Hi paul, I am nearly finished section2 of ebook and prem channel but stuck on this. I understand the transistor needs a base v+ to switch the primary, so ecu will send square wave to ignitor, like in this video. But I cant fiqure out how it works in a pull down fashion? If you had 12v at the ignitors and pulled down with a test light, how would that be providing a base signal at the ignitor transistor base? If you can point me to a section in your ebook that will make it easier for me to understand that would be awesome. Thanks so much, Edyn.

  23. i have a 93 ls400 and its running very badly… every thing i have found out about it (coil out seems to be the thing i keep finding out) and i was wondering the best way to test it… i would like to try this test but if the coil is out would this be a good test to try?.. would there be other things i should try?.. thanks for the help… i am out of work and dont have the ability to spend time or money without knowing for sure that its the reason… im going to have to borrow money from my girlfriend and thats bad enough… i need this car to help me find a job and get back on my feet and dont want to just walk away from it… thanks again

  24. Paul  on 2 wires coil test  if  install a jumper  from battery – to coil –  will that coilgenerate spark??

  25. I have a 1992 lexus ls400 yesterday my car windows ,dash lights,and ac went out on me but the car still did run but now today those problems are still plus it wont start it clicks like the battery is down but the battery is still good please help

  26. I have an uneasy feeling when you applied 12v to pull up. How about if the igniter only expected 2v, 5v, or 7v? Isn't it possible to supply too much voltage? I understand the pull up resistor will prevent too much current flow.

  27. AWESOME VIDEO!!!! I'm currently wiring a 1UZ into an old Datsun 280z and cant seem to get spark from either coil. I think this may help me quite a bit. Thanks!!

  28. i am melting my brain going between your book and the video. At 4:55–5:10 it seems like you are describing a pull down as being a pull up and vice versa. If the coils are sending voltage to the ecu and the ecu is pulling it to ground would it not be a pull up, next you describe it being a pull up if the computer is making a square wave(supplying a power) to the ignitor. would that make it a pull down instead?  im very sorry for the bother and i hope its not a dumb question

  29. I don't know if you will be able to help but it is worth a shot. I have a 92 ls400 and it is over fuelling like crazy. I had believed it to be the manifold (they were leaking) but after replacing them I'm still stuck with the same problem. Any ideas with where to start?

  30. Mr danner I try to fix a Lexus ls400 I have spark when I crank the engine and the fuel pump relay is not working is there anyway that I can jump start the relay terminals and see if the fuel pump work or how can I check the fuel pump voltage to determine if the fuel pump is bad

  31. i do have spark but i dont have 12 v At The fuel pump The fuel pump relay is burn and i just want to know how can i bypass to have power At the fuel and relay conection i dont even have a 2 second pulse or prime. so i have spark by using your method but no prime or no voltage At the fuel pump relay a little help will be apreciated thank you

  32. so been having no spark, coils are good ckp is good haven't checked cmp or icm so if the icm does not give the spark when given source voltage then the bad component will be the icm correct….. and if not will a cmp cause no spark?

  33. still have crank no start I did your by pass test I can hear the spark but there's no visual what would be the suspected component 93 ls400

  34. hey got spark my igniters were not bolted to my chasis so now im only getting spark with test light my ckp is new and cmp show good resistance value and my ecu was just verified good a couple weeks ago what can I do now also have no fuel only when jumped at b+ and fp diag port

  35. Hi mr danner I presently read your book I want to know if you send 12v with test light like video and its 5v control circuit or other like datalink?? It cannot be dangerous?

  36. from where will coil get 12v on igt wire incase of pull down design! because there is no positive voltage on coil.will there be a extra 12v feed voltage wire on coil or some capacitor inside of coil to make igt wire 12v

  37. Awesome video but i have a question on a 1995 Lexus ES300 with the same problem. My car only has a single igniter. I traced the wires and the igniter is getting power when the key is on but I don't know what wires to set the t-pins in to do your test. There are two banks of wires on the igniter; the one side (A) goes to battery positive, the 6 coils, and the data link connector. The other side (B) goes to the ground, 6 IGT wires, and an IGF wire. Help.

  38. even without using a voltmeter, but being a variable as you mentioned in one of your videos, for as long as you see two signal wires running to the computer, it is a pull up circuit design. Can this be said as a general rule of thumb?

  39. Sorry Paul, is been so long I can't understand this module to module communication,and I did my best to,however would like to clear my doubts before condemning something on the car,by applying power to two IGT igniter wires you simulate a good transistor inside in the igniter and if the coil fires we are going in different direction,here is my doubt,should we go in different direction??????What happens if igniters transistor that we simulated is actually bad and we should not go in different direction????

  40. solid video! nice to see expert advise with an thorough instructional video.
    I've been struggling with a 92 Ls400, did a water pump and starter replacement on it and now the rpm needle bounces when idling like its missing so I checked for codes and found none. Then I replaces spark plug wire's , cleaned distributor rotors and checks spark plugs all were good. Then I checked base timing it was good, can't seem to find the problem and the tranny wont shift any more under heavy throttle, just gets stuck and wont shift until you back off the throttle a little. So then I did a tran flush and filter replacement (using the correct fluid), needed to be done anyway's as the old oil was getting to the burnt side of things being almost purple. Still hasn't fixed any of the issues so now I'm left checking and cleaning grounds cuz I have no clue what else to do..

  41. Fantastic video that is currently helping me diagnose a no spark condition on my Toyota.
    In my case, the coil blew (visible damage) and it looks like it might have taken out the igniter, as replacing the coil did not fix the lack of spark.

    I supplied voltage to the IGT pin as you instructed, and the new coil did not fire.

    Is there any danger in supplying 12v through the test light to what is normally a 5v control signal on the IGT pin?

  42. I have this problem but I have 6 v to one igniter and 8 v to another can some one explain where to go from here

  43. Is this a common issue with a 1991 Toyota Previa? I'm having a no spark issue. I'm hoping this really can give me a solution.

  44. follow instructions to a tee. used test light and got spark to both coils. However when i crank there is no spark to either.

    got a new coils and crank sensor and still nothing. I am being told that i may have to check cam sensors?

    car was running well but had a starter issue for 2 weeks. on this day starter seem to have jump(loud noise) but car started ok.

    drove home and park and wont start when cranking. Timing belt was changed about 6 months ago.

    what is your suggestion? Located in the Bahamas and no certified or knowledgeable Lexus mechanic around.

  45. Hello, I am trying to register an account on your forum to ask for help in troubleshooting a P1300 OBDII code on a 1996 Toyota 4runner. I have yet to receive a confirmation email. Not sure if it just takes time but I figured I could give you an introduction here. I have been following diagnostic instructions in my Factory service manual but so far they all pass. There are a couple of results I am having trouble interpreting. Basically the engine dies at idle after a specific amount of time. According to the FSM if the ECU does receive a confirmation of ignition (IGF) signal after a number of IGT cycles then the fuel is cut. I have much more detail to add when I get access to the forum. Thank you.

  46. Hi, I have a problem with my corolla 93, recently my ignition coil fail in my car, i change it and ir work perfectly but now my car dosen't mark the RPM in my dashboard so my cuestion is, what can be the problem?

  47. What if I do this test exactly like you did and the test light lights up really dim when I touch the T pin and I don't get a spark from the coil?

  48. do you have any video of lexus Ls400 or 1uzfe engines injectors signal problems, my car have no power on the injectors when i crank the engine.

  49. I have 1999 four runner with a 3.4 liter engine runs great at an idle stop in the gas me sputters and does not want to create power but if you feather the gas pedal it creates power. It shows no codes when put on the tester also just put in a catalytic converter Any ideas on what the issue is?

  50. This is exactly what I was looking for with my No Spark. I'm still leaning toward CKP circuit, but this will definitely help me eliminate the igniters and coils! Thanks a bunch!

  51. I enjoyed the instruction on this post and it has helped to a point. I am working with a 96 Toyota Tacoma 2.7 liter with a no spark condition. I have tested continuity between crank sensor and ECM, between Igniter IGT B/L wire to ECM and performed the spark test by jumping with a test light 12v to the IGT by back pinning and received spark. What about a vehicle that has IGF safety signal, which if missing will cut fuel pump and spark?

  52. I am currently trying to diagnose my 1996 ls400, I have two codes reading p1300 and p1305. The only steps I have not taken was testing the coils, ecu, and the crank and cam sensors. The vehicle cranks but will not turn over, my question to this video is what wires do I stick the pins in with? The igt#1 is a black and white wire, and igt#2 is brown and yellow based off the diagram in your video. I wasn't sure if those were the wires I was supposed to test.

  53. I did exactly what you said on my 95 Lexus ls400 because I initially wasnt getting spark from the coil and was coming to the conclusion that my coils are bad but because of this bypass test i got spark to the coil. Im pretty sure its my cam or crank sensor but i have yet to test them to confirm. Anyway, thanks for this great video, really helped.

  54. I have a 1995 camry 4cyl 2,2, we replace the distribuitor assy and the igniter, after 30 minutes stalls again, whit same situation, I test the igniter the way you just did it, it looks good but just don't get spark what else could affect the ignition system???

  55. hi paul this is a good video, I am from venezuela and I have a lexus ls 400 of 92 my vehicle no crank no signal arrives at the coils, I tried to test the two modules but the voltmeter showed me more than 12 volts, and I could not see the spark coming out of the coils, I did not know what else to do since I do not speak English but I have a clear perception of what you teach, sorry if I do not write well, I am helping with the translator I need Your help to know how I can do to start my car. In my country there are few vehicles of this model. so I do not find a good technician with the necessary knowledge, everything that I have fixed to my vehicle I have done watching tutorial by you tube I would really appreciate it if you can help me

  56. Hey scannerdanner. I have a 1993 Toyota pickup with the old OBD and the DTC code that I get is telling that the ( igf signal from the igniter is not input to ECM for 6 consecutive ignitions ). can you me with that I would greatly appreciate it. thanks so much. further, the truck works but vibrates a lot. looking forward to here from you. Buy the way I have a career diploma as an electronic technician. that is why this video caught my attention so much, thanks.

  57. thanks for your tutorials.. they are easy to follow and very useful. i followed your ignitor trouble shooting vid yesterday on my 92 v8 soarer (it cranks n sounds like not firing n unsure if its getting fuel but i have bypassed the fuel pump and could hear a flow so i dont think its a fuel problem… i hate to admit but i was jump starting it and accidentally let the jumper leads touch n since then its a crank n no start cond. yesterday when checking ignitors i did confirm decent spark from one but not the other. i wasnt sure if maybe i didnt probe the wire properly and tried a few more times. then we decided to try plugging them in oposite because i could easily get a good probe one the one that seemed fine…..AND THEN… i couldnt get either to spark at all… should i not have plugged them in oposite?? it was cold and dark so i may have just not had good contact with probe wire. im going back to try again in the morning and thought i best check incase im flogging a dead horse??

  58. Dear sir my car is Camry 1993 before there wasn’t spark on ignition coil but after i did your way by test light on igniter pin IGT white color wire its responding to start but again cut off what’s could be issue please help

  59. I have 93 Lexus LS-400….only running on 4 cylinders….no spark to plugs from drivers side Distributer….has spark from coil going into Distributer but nothing coming out of Distributer..changed rotor..cap..still same…spark from coul wire very small and almost have to touch coil wire end directly to get spark….coil tested ok at AutoZone with meter at 200 ohms…is it possible for coil to bench test ok but not put out enough voltage?

  60. Can someone help me? I tried the diagnosis by danner above, however, I still have an igniter for the right side that will not fire. I have battery voltage to the igniter, and the coil in question. I have good ohms from the 6 pin on the igniter to the coil. I have tried to use the good igniter from the left side with no avail. I have tried the left good coil wire on the right coil. . I have swapped igniters. any ideas? Simply put…I put the good igniter, coil, and wire on the bad side…no avail.

  61. Awesome explanation and display of knowledge. Any tips on how I can develop that type of critical thinking. GOD BLESS

  62. I have a 1988 Camry That isn’t getting any spark I would like to know if the ignitor in this car has to be grounded in order for it to start? This is a derby car that ran fine until I moved all of the wiring harnesses into the fire wall area of the car

  63. In theory, couldn’t you just touch one end of a wire to the + side of the battery and the other end to that pin for the igniter? Wouldn’t that accomplish the same thing as the T pin and test light probe??

  64. Would this be more chapter 3 and power side switching? I thought pull up was with inputs. The ecu seems to be controlling the igniter and not really “watching”. My brain is fried from binging on the premium channel (BrannonG92) so I am still probably confused a bit. I really want to master chapters 2 and 3 before moving on any further!

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