P0372 and P1371
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Joined: Mar 2008
Posts: 97
He stated in the first post it's not running.
Thread Starter
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Joined: Feb 1999
Posts: 360
From: Rio Rancho, NM
Alright...so I'm getting like .15 volts while cranking. Hence the low res signal code P0372.
Getting the 12 volts on A and D. Ground is sound.
Can I check signal from the opti to the PCM at the Opti Pigtail at all??
My next move is taking the opti out again right??? Just hoping that there is a way to test to confirm...
Unless it could be the PCM....all fuses check SAT.
Lemme know fellas,
Ivan
Getting the 12 volts on A and D. Ground is sound.
Can I check signal from the opti to the PCM at the Opti Pigtail at all??
My next move is taking the opti out again right??? Just hoping that there is a way to test to confirm...
Unless it could be the PCM....all fuses check SAT.
Lemme know fellas,
Ivan
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Joined: Apr 2004
Posts: 1,046
From: Fargo, ND
I believe what you just did is similar to the test noids on the injectors. Do you have access to them?
I bought a set from advanced for IIRC under 15$. Anyway, after the test you just did I believe me our cars have the same problem.
My car has been down for months
So I am hoping they can help you here!
I bought a set from advanced for IIRC under 15$. Anyway, after the test you just did I believe me our cars have the same problem.
My car has been down for months
So I am hoping they can help you here!
Thread Starter
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Joined: Feb 1999
Posts: 360
From: Rio Rancho, NM
You know, I've had multiple people tell me that is what it could be. But a few of the fellas that I look up to here assured me that the CPS only accounts for "small adjustments to timing and not actual starting of the car."
At this point is probably worth a shot to try but I am sick of throwing money at a part, waiting for it to come in, spending one of my only days off to pull it out of the garage and install it......only to not have any luck with it.
I've been trying so hard not to have it taken into the GM shop but at this point, my time is worth alot. So the more that I FAIL to get something to work, the more I tell myself to just start saving up so that I can take it in.
Maybe it's worth it since it's pretty much the only part that I haven't replaced....I don't know.
Thanks for helpin,
Ivan
At this point is probably worth a shot to try but I am sick of throwing money at a part, waiting for it to come in, spending one of my only days off to pull it out of the garage and install it......only to not have any luck with it.
I've been trying so hard not to have it taken into the GM shop but at this point, my time is worth alot. So the more that I FAIL to get something to work, the more I tell myself to just start saving up so that I can take it in.
Maybe it's worth it since it's pretty much the only part that I haven't replaced....I don't know.
Thanks for helpin,
Ivan
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Joined: Mar 2008
Posts: 97
CPS is for detecting misfires only, it has no bearing on engine operation. Are the injectors firing? if not, the PCM is not getting the low res pulse. This could only mean the OPTI or the harness to it, or the PCM itself.
The PCM sends 5v reference signals to the opti, one for the low res and one for the high res. When the disk in the opti spins, the sensors ground that 5v signal. The PCM detects the circuit is grounded, then open, then grounded, etc. and this is how it gets the input from the opti. You can see this with an Oscilliscope, but if the injectors are firing, this is an easier way to see if the PCM is seeing the opti function properly.
The PCM sends 5v reference signals to the opti, one for the low res and one for the high res. When the disk in the opti spins, the sensors ground that 5v signal. The PCM detects the circuit is grounded, then open, then grounded, etc. and this is how it gets the input from the opti. You can see this with an Oscilliscope, but if the injectors are firing, this is an easier way to see if the PCM is seeing the opti function properly.
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Joined: Apr 2004
Posts: 1,046
From: Fargo, ND
I am speaking for myself and I believe him also, no the injectors are not firing.
We have both installed new opti's, and have no spark anywhere in the ignition system.
For us both to have bad GM opti sounds crazy, yet somehow feasible I dont want to believe it is the opti again!
How do rule out the PCM?
Iprice correct me if I am wrong on anything above.
We have both installed new opti's, and have no spark anywhere in the ignition system.
For us both to have bad GM opti sounds crazy, yet somehow feasible
I dont want to believe it is the opti again!How do rule out the PCM?
Iprice correct me if I am wrong on anything above.
Thread Starter
Registered User
Joined: Feb 1999
Posts: 360
From: Rio Rancho, NM
CPS is for detecting misfires only, it has no bearing on engine operation. Are the injectors firing? if not, the PCM is not getting the low res pulse. This could only mean the OPTI or the harness to it, or the PCM itself.
The PCM sends 5v reference signals to the opti, one for the low res and one for the high res. When the disk in the opti spins, the sensors ground that 5v signal. The PCM detects the circuit is grounded, then open, then grounded, etc. and this is how it gets the input from the opti. You can see this with an Oscilliscope, but if the injectors are firing, this is an easier way to see if the PCM is seeing the opti function properly.
The PCM sends 5v reference signals to the opti, one for the low res and one for the high res. When the disk in the opti spins, the sensors ground that 5v signal. The PCM detects the circuit is grounded, then open, then grounded, etc. and this is how it gets the input from the opti. You can see this with an Oscilliscope, but if the injectors are firing, this is an easier way to see if the PCM is seeing the opti function properly.
Or am I swinging with a football bat?? LMAO...
Thanks,
Ivan
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Joined: Mar 2008
Posts: 97
No, the PCM fires the injectors based on the low res pulse from the opti. If the injectors are pulsing, then the opti is sending the low res pulse. If the injectors are not firing, then the PCM is NOT getting the low res pulse.
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Joined: Mar 2008
Posts: 97
You could unhook any injector, then use a test light connected from one pin to the other on the injector plug you took off. Now crank the engine. If the test light blinks on and off while cranking, then the opti is atleast sending out the low res pulse to the PCM. If you have between 1-4v on the ICM per SHoebox's site, this also confirms the PCM is getting the low res pulse and is telling the ICM to fire the coil. If this all checks, then see if the coil is firing by unhooking the coil wire from the opti and cranking to see if it sparks using a spark tester, or just grounding it with a screwdriver to see if it sparks. If this checks, then see if the opti is sending the spark back out to the plugs, by unhooking a plug wire and seeing if it sparks while cranking. If all of this is good, then the engine should run. If not, tell us which test failed and we can try to help from there.
Thread Starter
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Joined: Feb 1999
Posts: 360
From: Rio Rancho, NM
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Joined: Mar 2008
Posts: 97
I'm not sure if this is showing you if the injectors are firing. You can test your light by touching the + on your battery to - to see if it lights up. On the injector plug, one side is hot with the key on at all times. The other wire provides a ground only when the PCM tells that injector to fire, ie while cranking.
Thread Starter
Registered User
Joined: Feb 1999
Posts: 360
From: Rio Rancho, NM
I'm not sure if this is showing you if the injectors are firing. You can test your light by touching the + on your battery to - to see if it lights up. On the injector plug, one side is hot with the key on at all times. The other wire provides a ground only when the PCM tells that injector to fire, ie while cranking.
It seems like the injectors might be firing since the voltage varies with cranking. But I'd like to make sure and do it with a light to confirm. And if they are firing, then we know the PCM is sending the low res signal.
But it wouldn't make sense that the injectors are seeing the low res signal and the icm/coil are not unless there is issue in the wiring between the PCM and the ICM right??? I replaced the pigtail piece to the ICM but there could be issue further "upstream" I suppose.
I'll get the light on it and confirm.
Thanks for the time,
Ivan
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Joined: Nov 1998
Posts: 71,094
From: Hell was full so they sent me to NJ
You can't verify injector operation with a DC volt meter or a simple test light. The fact that the voltage varies would infer that there is a ground being supplied by the PCM proportional to the pulse width. But a conventional test light will not respond fast enough. You need a "noid" light, that plugs in between the harness connector and the injector, and has a rapid response to the very short pulse width that the PCM sets. You can get a set of 'noid lights very cheap at places like Harbor Freight.
If the PCM is setting P1371, its telling you it can't find the low resolution pulse from the Opti.
If the PCM is setting P1371, its telling you it can't find the low resolution pulse from the Opti.