using the FSM saved me money
04-10-2016, 12:22 PM
#1
Advanced
Thread Starter
using the FSM saved me money
A while back I noticed that my 92 LT1 started running rich so bad at idle that it reminded me of sitting in traffic in he 70's as a kid amongst the old carbureted stinkers and the engine wanted to stall when I put it in gear when the engine was below 100*. The first thing I thought was why there wasn't an SES light on my DIC panel. I pulled out my FSM and did some research and found out that the bulb was burned out, so I followed the procedure in the book and disassembled the dash and replaced the tiny bulb, all of which was laid out in the manual step by step. Even the bulb part # is in there so when you get to the parts store you will already know what you need.
I then was able to pull the codes from my ECM and found that I had the following codes.
16 opti spark low resolution pulse
26 quad driver module circuit 1
43 electronic spark control(ESC) circuit fault. Knock sensor circuit.
The good thing about the FSM is that it describes the system for what the fault code is set in and how to step by step diagnose the problem.
I had removed the AIR injection system earlier and since the pump was removed that is what was causing the code 26 since circuit is looking for a voltage signal when the pump turns on.
It seemed coincidental that 16 and 43 where related due to fact that they are both part of the ignition system.
I cleared the codes and started the engine. 43 set right away and after a short drive 16 came back.
I performed the diagnostic procedure for code 43 and found that I had good voltage to the wire and that they were not shorted or open. I then checked the resistance of the knock senors that were supposed to have an ohms reading of 3500 to 4500 ohms and I was getting 13000 on one side and 15000 on the other and thought that I had 2 bad senors and the cheapest I found them were 38 bucks ea at advance so I would be spending over $80 to fix the my problem. BUT!!!!
In the fault tracing section for code 43 one of the last steps was "faulty sensor or faulty knock sensor installation" Hmmm that's interesting, 2 bad sensors? The car is over 24 yrs old so it could be possible but unlikely. I've been working on GM based marine engines for almost 30 yrs and seen maybe 1 bad knock sensor in my time. I looked up the torque spec for the sensor which of course is located in the trusty FSM and retorqued both senors, rechecked the resistance and both senors read 3900 ohms which is well within spec. I cleared both codes again and have put close to 100 miles on engine and no SES light has come back on,no more rich stinky exhaust or idle rpm drop when put in gear and I didn't have to shell out 80 bucks for parts.
As others have pointed out on here, get a copy of the factory FSM for your year model C4 whether it's the cd or the paperback version. It will save you money when used properly. I would also recommend that you watch the videos put out by 93rubie lots of good info there.
I then was able to pull the codes from my ECM and found that I had the following codes.
16 opti spark low resolution pulse
26 quad driver module circuit 1
43 electronic spark control(ESC) circuit fault. Knock sensor circuit.
The good thing about the FSM is that it describes the system for what the fault code is set in and how to step by step diagnose the problem.
I had removed the AIR injection system earlier and since the pump was removed that is what was causing the code 26 since circuit is looking for a voltage signal when the pump turns on.
It seemed coincidental that 16 and 43 where related due to fact that they are both part of the ignition system.
I cleared the codes and started the engine. 43 set right away and after a short drive 16 came back.
I performed the diagnostic procedure for code 43 and found that I had good voltage to the wire and that they were not shorted or open. I then checked the resistance of the knock senors that were supposed to have an ohms reading of 3500 to 4500 ohms and I was getting 13000 on one side and 15000 on the other and thought that I had 2 bad senors and the cheapest I found them were 38 bucks ea at advance so I would be spending over $80 to fix the my problem. BUT!!!!
In the fault tracing section for code 43 one of the last steps was "faulty sensor or faulty knock sensor installation" Hmmm that's interesting, 2 bad sensors? The car is over 24 yrs old so it could be possible but unlikely. I've been working on GM based marine engines for almost 30 yrs and seen maybe 1 bad knock sensor in my time. I looked up the torque spec for the sensor which of course is located in the trusty FSM and retorqued both senors, rechecked the resistance and both senors read 3900 ohms which is well within spec. I cleared both codes again and have put close to 100 miles on engine and no SES light has come back on,no more rich stinky exhaust or idle rpm drop when put in gear and I didn't have to shell out 80 bucks for parts.
As others have pointed out on here, get a copy of the factory FSM for your year model C4 whether it's the cd or the paperback version. It will save you money when used properly. I would also recommend that you watch the videos put out by 93rubie lots of good info there.
Reading FTW. Way better than throwing $$$$$ at a problem.
04-11-2016, 05:07 PM
#4
Safety Car
Glad you used your resources and brain to fix a problem instead of guessing and throwing money at it!!! Thanks for the kind words!
The OP did exactly what one SHOULD do. Read, learn, and do. Don't guess, it costs you. Ignorance might be bliss but it is NOT cheap.
@JackRidley, (sarcasm) Reading....understanding how something works....ain't got no time for dat!!! Just tell me what part to replace!!!
The OP did exactly what one SHOULD do. Read, learn, and do. Don't guess, it costs you. Ignorance might be bliss but it is NOT cheap.
@JackRidley, (sarcasm) Reading....understanding how something works....ain't got no time for dat!!! Just tell me what part to replace!!!
04-11-2016, 07:58 PM
#5
Burning Brakes
Where do you buy a digital version?
and...
just to be an smart ***...
you spent $275 on a book to save $80 in parts.
I know it will pay for itself over time. I could not resist.
and...
just to be an smart ***...
you spent $275 on a book to save $80 in parts.
I know it will pay for itself over time. I could not resist.
Last edited by 2ooo-C5; 04-11-2016 at 07:59 PM.
04-11-2016, 09:03 PM
#6
Advanced
Thread Starter
You can find a cd rom version on flea bay but I find the paper version easier to navigate.
Ive been working on various types of machinery and engines as a marine mechanic for almost 30yrs and believe me knowledge is a valuable tool in getting the job done right and efficiently.