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 96 Riv ignition Fault Issue

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Rodman
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Name : Rod
Location : Southwestern Ontario
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PostSubject: 96 Riv ignition Fault Issue   Sun Sep 26, 2010 7:12 pm

Hello guys,

|I am having a bit of a problem with my 1996 3.8 supercharged Series II riv. i just bought it after driving an 83 Regal for the last 6 years. I like the buicks. I am new to fuel injection and am stumped on this problem.

I have run a snap on scanner on it, and it shows the car has "Ignition mode: yes", which from my understanding means the Ignition control module is controlling the timming of the engine at 10 degrees (should read Ignition mode: no, which it reads when the key is on, but turns to yes when car is running). It is suppose to have the Power control module (PCM) controlling the timming but their is a igntion fault that I cannot track down.

The service engine light is not on, and their is no codes present. I have entered the following codes to test, but they show no history of ever occuring;
P1350
P1361
P1374
P0341
P0336


Any guidence would be appreciated.

thanks,

Rod

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Abaddon
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PostSubject: Re: 96 Riv ignition Fault Issue   Sun Sep 26, 2010 7:48 pm

Not quite sure what you're looking for, but here's the schematic for the ICM.


Codes P1350 & P1361 will set if there is a problem with CKT 423 (Wht) and CKT 424 (Tan/Blk).

Is the car running funny? Is it stalling randomly?

The ICM controls Ignition timing during engine cranking. After it starts, and the 3x Ref is received by the PCM, the PCM applies 5 volts to the Bypass Circuit, which commands the ICM to surrender control of spark advance, and the PCM takes over.

Again, not sure what ur looking for..
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Rodman
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PostSubject: Re: 96 Riv ignition Fault Issue   Sun Sep 26, 2010 8:24 pm

Abaddon,

Thanks for the diagram. To try to clarify my first post, what I am looking for is to the reason why the PCM is not taking control of the ignition from the ICM while the car is running.

The car is running fine, it starts easy, drives nice seems to have plenty of power. However, the scanner is showing that the PCM is not controling the ignition while car is running. This is what I need to fix and i am usure of what is causing this problem as their is no codes or history of codes to show what is defective.

I don't think this matters, but i just fixed a P0300 random misfire in cylinder 5. The injector was blocked with rust/junk. I replaced the injector and installed a new gas filter. Verified problem fixed with scanner.

Abaddon, what does 3x reference and 18x reference mean and is the bypass just a wire?

Any ideas on this ignition fault is appreciated,

Rod
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Abaddon
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PostSubject: Re: 96 Riv ignition Fault Issue   Sun Sep 26, 2010 8:47 pm

I think you are mistaken Rod. I believe Ignition Control "Yes" means the PCM is controlling Ignition Timing. If there were a problem with that circuit (424 or 423), a code would be set (P1361 Ignition Control Circuit Not Switching, or P1350 IC Bypass Circuit)....the SES light may or may not come on, but a code should certainly show up as history.

P1350 would set if the ICM doesn't receive 5v from the PCM on CKT 424
P1361 means that the PCM is not gaining control of spark
advance from the ICM through CKT 423, which needs CKT 424.

got me?

Unless any codes are set, current or history, I'd say your car is fine. If any one of those circuits (423 or 424) had a problem, a code would set, and you may end up with totally random stalls.
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Rodman
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PostSubject: Re: 96 Riv ignition Fault Issue   Tue Sep 28, 2010 9:10 pm

Abbaddon,

I'm picking up what your putting down. You must be right, because i have looked into everything I think I could. I was going by troubleshooting data on the scan tool that said it should read no. But the car runs fine, so I am going to leave it alone. I am assuming I would notice a drop in drivability if the PCM was not in control?

Thanks for the quick responces and helpful knowledge
Rod
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Abaddon
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PostSubject: Re: 96 Riv ignition Fault Issue   Tue Sep 28, 2010 11:00 pm


I'll go back to your previous post in order to make sense of it all, and answer your previous questions.

The 3x reference is a signal produced by the ICM. This signal is received by the PCM and is used to calculate RPM's, and also Crankshaft position above 1200rpms. The PCM uses these pulses to initiate Fuel Injector pulse.

The 18x reference is produced by the CKP sensor, which is filtered by the ICM, and then sent to the PCM. The PCM uses this information to calculate engine speed and CKP position at speeds less than 1200rpms.

The ratio of 18x (CKP) pulses to 3x (ICM) pulses must equal 6.
The ratio of 3x pulses to CMP pulses must equal 6.
When the PCM has all of this information (CKP, CMP, ICM), it can then control spark advance accordingly.

Yes, the Bypass circuit is a "just" a wire that carries 5v, which is sent by the PCM to the ICM. An open in the IC Circuit or a short to voltage on the Bypass will set P1350. A short in the IC circuit, or an open or short to ground on the Bypass will set P1361. Either one of these codes results in the PCM not gaining control of spark advance.

When the PCM receives and recognizes the second 3x pulse during cranking/starting, it then applies the 5v to the Bypass circuit, and commands the ICM to "give up" control of spark advance. The is referred to as IC mode. This, I'm assuming is what your scanner meant by "Ignition Mode: Yes". This is the correct reading you should get. IC Mode: Yes actually means that the PCM is in control of spark advance. If the PCM does not gain control of spark, you would more than likely have driveability concerns, and again, random stalling.
I'd get more into why the driveability concerns would exist, but trying to explain the way a PCM thinks is a bit tricky, and I'm not stoned enough to dive into that rabbit hole.....either way, a code would be set in the event of a problem with that (those) circuits.
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