I have trying to fix this error for about 6 months now. I have replaced:
both knock sensors with the correct one (part number ac delco 213-268)
checked the wiring from the sensors all the way back to the PCM
replaced the PCM
even bypassed the wiring of the car and used new wire - running it from the sensors directly to the pcm.
I am still using the original PROM from the old computer. Using a scan tool meter, the PCM will see a knock sensor signal around 3,000 rpm or higher - but it isnt a constant signal. Knock retard will go to 10 and stay there. Starts off a 0.
I was thinking about getting a new PROM flashed with the latest software to see if this might fix the problem, but I am all out of ideas. Hate to take it to a dealer and have them replace all the stuff I have already replaced and charge me a few thousand dollars. It has to be something simple I am missing.
Replaced the connector. Checked with a multi meter to make sure I had a connection from the end of the connector to the PCM. One thing I failed to mention - the original motor died so it was replaced with a 3800 series II engine out of a 98 buick lesabre.
April, 29, 2012 AT 1:16 PM
The sensors have different part numbers. Did you put the original one back from your motor?
April, 29, 2012 AT 1:40 PM
Unfortunately not, the original motor was a COMPLETE lost cause. I have been reading around that I MIGHT have to take the car to the dealer and have the PCM relearn the sensors of this motor. Not sure if this is true or not.
April, 29, 2012 AT 1:56 PM
No, it is not correct. There is no re learn for obd 1.
Try getting the original knock sensor and see what happens. The gm number is 10456215
April, 29, 2012 AT 3:48 PM
Tried that. The 10456215 part number crosses over to a acdelco 213-268. Still doesnt work. The car's PCM isnt a OBD 1 it is a OBD 1.5 (that odd 95 year that GM only used this - it has a OBD 2 connector but only certain scan tools will read this car)
April, 29, 2012 AT 3:50 PM
Yep, it is a cross over to obd 2. I see no flash updates available for this.
Do you have a scan tool?
April, 29, 2012 AT 3:57 PM
Yup. The scan tool will read a knock signal every once in a while. But nothing constant. Knock retard is at a constant 10. Never goes to 0 unless the car is off.
April, 29, 2012 AT 4:43 PM
Try tappin the motor with a hammer. It should change.
The retard works from going 4 degrees to a max of 12 to try and get rid of the harmonics it hears.
Is there any valve train noise or lower end noise? If you disconnect it, does the timing stay constant?
April, 29, 2012 AT 6:21 PM
Tapped the motor close to the sensor (not the sensor) and the scan tool sees and records the pulse each time I do it. The retard never changes. If I disconnect the sensor, the timing does stay constant. No valve train noise and the engine runs VERY quiet.