The crank sensor was replaced, and I took the car to get a relearn, but the mechanic said that the car wouldn't take it. He made 2 attempts at a relearn without success. He was even revving up to nearly 5000 rpm with no luck. Immediately after trying the relearn, we checked the fuel trims, and they were all within a + or - 10 range. I can work on graphing the O2 sensors. How do you measure the quality of power and grounds?

 

The crank sensor relearn may be the whole issue. What brand of sensor did you use? Based on this I am going to change my suggestion to checking the power and ground to the crank sensor first. With the sensor still hooked up back probe the lt grn and ppl wires and measure the voltage at key on then watch the voltage while the truck is running, it should be rock solid, its a controlled reference voltage. Watch your wires down there. Do you have a scope?


George

 

I can't remember what brand sensor it was but I don't think it was an AC delco part. I have a wire probe that lights up when there's voltage. Is this the scope you're talking about?

 

No, I meant oscilloscope. that’s a rare animal for do it yourself is but I thought I’d ask just in case you were an electronics guy that way we could look at the crank sensor waveform and make sure it looks OK. I don’t think We should go any further than this crank sensor situation until we get that straightened out since that’s fundamental to misfires George

 

The Vident ilink400 is a fan favorite around here. It can do the crank relearn, brake bleed, …

George

 

Another thing I forgot to mention. Remove the crank sensor and look for signs that it’s hitting the relict or wheel. If so, it needs to be shimmed. A shim may help regardless but a relearn is still required.


George

 

So I managed to find an ilink 400 and I attempted another crank relearn just to see what happens same thing, wouldn't relearn. Tonight, I'll try to back probe the sensor and check for interference with the reluctor. I want to confirm that to back probe, one terminal of the multimeter probes the light green wire while the other terminal of the multimeter probes the purple wire.

 

Found this. Mabe help? Dunno....

 

Normally, reluctor/sensor interference is determined by pulling out the sensor and looking for contact. What brand of sensor did you use?

George

 

I consulted with Les on this issue which resulted in this advice:

CASE relearn trouble

1. Shut engine off fully warmed up
2. Turn key on (don't turn off until done)
3. Depress parking brake just enough to turn the brake light on (don't turn off until done).
4. Clear all codes, including pending codes.
5. Hold brake pedal down with left foot (don't let up until done)
6. Start engine and immediately do CASE relearn.

If you wait until a pending or hard misfire code is set again, the relearn will not activate and do the fuel cutoff.


George