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96 lexus ls 400 no spark

posted May 22, 2016 00:57:02 by Ken Carroll
96 lexus ls400 no spark no injector pulse did igniter check and both coils spark ohm'd both cam sensors good crank sensor ohm'd good snap on scanner no communication getting 12 volts to odb connector and ground there is 12 volts going into ECU and ground i have pinout of ecu pins but mitchells is lacking after sensor checks if still no fire. any help would be appreciated
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15 replies
cheryl hartkorn said May 22, 2016 01:29:40
do you have a 5 volt reference at a tps or maf sensor? key on.
cheryl hartkorn said May 22, 2016 01:30:12
also does the check engine light come on during a bulb test?
Ken Carroll said May 22, 2016 10:18:50
Have not checked the volts there yet but yes the check engine light is on I will check that in the morn trying to get all the info I can and go from there if there is volts there what should I check next? If there is no volts there then what is the next step?
PaulDanner said May 22, 2016 11:49:24
Agree with Cheryl. Check your reference circuit next. This will tell us if your computer is alive or not. The no com issue may or may not be related to your problem. Also the ohm test for cam and crank sensors is not an accurate test. You need to measure the output voltage of these sensors. But let's address the reference problem first.
RassielCotoMedina said May 22, 2016 11:53:05
if no 5 volt reference next step is power and ground to pcm and if they are there, voltage drop test to pcm
PaulDanner said May 22, 2016 12:13:04
if no 5 volt reference next step is power and ground to pcm and if they are there, voltage drop test to pcm

Agree and don't forget about a shorted sensor pulling the reference circuit to ground
Ken Carroll said May 23, 2016 12:49:52
Ok 5 volt reference to tps and maf also had 12 volts and 12 volts ground to each connector ---volts at computer is almost identical to battery volts during cranking it does drop to below 10.50volts? Battery is brand new doing a cam and crank signal wave form check now
CyrusKiur said May 23, 2016 13:23:25
I think if u have scannerdanner ebook its very simple to trouble shoot the problem.first start with checking cam and ckp signals,second check whether all ignation coils and injectors have 12 volt (koeo)or (koes)
Ken Carroll said May 23, 2016 14:57:07
ok I have 5 volts to tps and map doing a pinout of ECU this is what I have pictures included ok at the idle 2 e14 pin 31 it has 12 volts at computer terminal I plug in connector and the wire gets a ground instead of 12v + going out of it I unhooked tps Maf coolant temp sensor egr sensor and the wire is still showing a ground brown wire I am doing something wrong ?
Ken Carroll said May 23, 2016 14:58:46

Ken Carroll said May 23, 2016 15:02:39
If I'm reading this right pin 31 at ECU works all the sensors? please help before a Lexus catches on fire and burns
Ken Carroll said May 23, 2016 17:57:38
Only getting 0.54 volts to e14plug 12 pin for igt1 wire at computer where Mitchell says 4.50-5.00volts both crankshaft and camshaft sensors have 12 volt ground to both terminals since these are a 2 wire connector should one be getting + volts? Even cranking neither wire gets + voltage
Noah said May 23, 2016 23:42:51
Ok 5 volt reference to tps and maf also had 12 volts and 12 volts ground to each connector

Hey Ken, I'm confused here, are you saying there's 12v on the 5v ref circuit? I'm also not sure what you mean by "12 volts ground".

Not picking, but universal standardized terms helps keep everyone on the same page.

You are right, pin 31 is the 5v ref source for egr temp, coolant temp, maf and tps. Won't burn down anything with 5všŸ˜‰. So at pin 31,(and the brown wire of those sensors) you should have 5v with the key on.

You should have 12v on both pins 1 and 2 of each coil with the key on and 12v on 3 and 5 of each igniter with the key on.

Pin 2 on each igniter is the turn on signal or control wire. I can't tell from the diagram if you should expect to see pulsed 5v, pulsed 12v, or pulsed ground while cranking to "turn on" the transistor in the igniter.

As for the cam and crank sensors, I don't see them on the diagram. Since you say they're 2 wire sensors, they may be of the AC generating variety. Meaning they create their own AC signal while cranking(or running). So in that case, with the sensor connected and the engine not cranking, I wouldn't expect to see any voltage.
Hope this is helpful.
Massachusetts, USA
RassielCotoMedina said May 26, 2016 13:56:19
it looks like a shorted sensor cause you say you have 5 volts with the wire unplugged, start disconnecting sensor untill the 5 volts come back when it does thats your sensor remember to leave unplugged every sensor you dissconnect just in case the is more than 1 sensor shorted
Ken Carroll said Jun 08, 2016 01:01:18
Well sorry for confusion but I sent the computer out for repair and the car cranks and I can communicate with my scanner so the computer had bad capacitors and acid on the board I had it repaired for 70 bucks with 10 shipping the igniter text from Scannerdan helped eliminate the coils and igniter
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