PCM Failures
08-11-2010, 11:49 PM
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PCM Failures This is an odd one that no one can diagnose..
I have gone through 3 PCM's just to verify this problem, and right now have 2 "functional" PCMs that work in other cars just fine...
The problem: Code 43, and Left O2 sensor readings wacky.
Code 43 means that the knock sensor circuit is open, however, I can easily read a voltage to the sensors wires, they have good ground, the sensors work fine, and the resistance is perfect. However, code 43 still is there.. Car runs fine otherwise, just pig rich and 9mpg because it goes clearly into Limp Home Mode.. It's been running like this since 2001...
If I go into the PCM and reflash it with code 43 disabled (and thus the KS check), it will manage to finally actually start using closed loop properly and make fuel table adjustments (it doesn't in limp home, despite being in closed loop, BLMs stay at 128), however every time I come to a stop, the car nearly stalls, or hesitates.. I replaced the O2's, but that doesn't solve it either..
In a datalog, I found that the right O2 sensor voltage reading is perfect, but the left is spazzing out badly.. I then in one morning, decided to turn the PCM on but not the car, keeping the car and O2's cold, and read them again.. They both should be low and lazy as no oxygen is passing them, nor are they hot just yet.. Left sits low at like 20mV like I expect, but the left is spazzing out like the engine is running, hitting as high as 1000mV...
I figure these two problems are related to each other somehow, and perhaps, ground related, despite the sensors having good ground to the engine block.. I'm thinking along the lines of, one of the many grounds on the PCMs pinout, are faulty and the cause of the problem..
Which ground pin on the PCM are responsible for these two sensors?
I can say this though, the 2 knock sensors, are tied together to the same pin, so both are affected by this nonsense..
Oh, and before I end this crazy and exciting thread, I did this as a test.. I cut the O2 sensor wires going to the PCM, both of them, to force the PCM into reading a dead signal.. Right O2 readout, just like it should, completely dead. Left signal, holy crap, it's still bouncing despite the PCM having NO wire at all to that sensor!
Once again though, I replaced the PCM many times and now have 2 PCMs that work fine on any other car..
Just the big two battles I've been having with this car..
I have gone through 3 PCM's just to verify this problem, and right now have 2 "functional" PCMs that work in other cars just fine...
The problem: Code 43, and Left O2 sensor readings wacky.
Code 43 means that the knock sensor circuit is open, however, I can easily read a voltage to the sensors wires, they have good ground, the sensors work fine, and the resistance is perfect. However, code 43 still is there.. Car runs fine otherwise, just pig rich and 9mpg because it goes clearly into Limp Home Mode.. It's been running like this since 2001...
If I go into the PCM and reflash it with code 43 disabled (and thus the KS check), it will manage to finally actually start using closed loop properly and make fuel table adjustments (it doesn't in limp home, despite being in closed loop, BLMs stay at 128), however every time I come to a stop, the car nearly stalls, or hesitates.. I replaced the O2's, but that doesn't solve it either..
In a datalog, I found that the right O2 sensor voltage reading is perfect, but the left is spazzing out badly.. I then in one morning, decided to turn the PCM on but not the car, keeping the car and O2's cold, and read them again.. They both should be low and lazy as no oxygen is passing them, nor are they hot just yet.. Left sits low at like 20mV like I expect, but the left is spazzing out like the engine is running, hitting as high as 1000mV...
I figure these two problems are related to each other somehow, and perhaps, ground related, despite the sensors having good ground to the engine block.. I'm thinking along the lines of, one of the many grounds on the PCMs pinout, are faulty and the cause of the problem..
Which ground pin on the PCM are responsible for these two sensors?
I can say this though, the 2 knock sensors, are tied together to the same pin, so both are affected by this nonsense..
Oh, and before I end this crazy and exciting thread, I did this as a test.. I cut the O2 sensor wires going to the PCM, both of them, to force the PCM into reading a dead signal.. Right O2 readout, just like it should, completely dead. Left signal, holy crap, it's still bouncing despite the PCM having NO wire at all to that sensor!
Once again though, I replaced the PCM many times and now have 2 PCMs that work fine on any other car..
Just the big two battles I've been having with this car..
08-12-2010, 01:03 AM
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http://www.camaroz28.com/forums/showthread.php?t=685699
That guys problem seems like it could have been related to mine.. Left O2 reading odd, and code 43..
I'm gonna attempt tomorrow to figure this out, in the morning.. Probe more ground lines..
That guys problem seems like it could have been related to mine.. Left O2 reading odd, and code 43..
I'm gonna attempt tomorrow to figure this out, in the morning.. Probe more ground lines..
