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P1391

1K views 7 replies 4 participants last post by  herbS 
#1 ·
Have persistent p1391 after replacing crank sensor, cam sensor, cap & rotor. Any suggestions?
 
#4 ·
What year and engine is this?

On a gen 2 ('97-'04) (& this may apply to other years, but I am not familiar with them is all) the crank position sensor (& I believe the cam position sensor also) get their power (I think I remember that being 5V) from the PCM. I suppose it would be possible that if the PCM wasn't sending the proper voltage to either of those sensors that could generate the code, but TBH, I am not sure if it would even start if that was the case. I'll paste the instructions (from another thread) for checking at the crank position sensor below (& these instructions were for a gen 2-'97-'99 group- 3.9/5.2/5.9).

"The crank sensor on tranny bell housing gets its power from the pcm. If you want to check the crank sensor proceed as follows:
Find the crank sensor at back of engine. Get a multimeter and hook it (wire probe) to the wires of the crank sensor.
Disconnect your fuel injector harness if you do this test before emptying tank.
Turn key on then MANUALLY turn over engine at the crank pulley with a 1/2" breaker bar.
You should be getting an "on-off" signal of around 5 volts.
If you get this signal, its your pcm which also goes south on these things quite frequently.

Disconnect the coil before this test is done as well and DO NOT remove the crank sensor for this test. It can stay right there.
On the tranny housing, locate the c sensor and strip off enuf wire (black/grey) to connect your m meter red wire to this. Your meter should be in " dc volt" mode . Connect your black m meter wire to any good ground.
Have someone flip over the engine w the breaker bar and notice if you're getting a voltage reading.
The reason you manully turn over engine is to not get a false signal that the starter motor can cause.
Now if you're getting this signal, then you know its not the sensor. If you're not, you could have a bad ground here so clean up this connection first before we accuse the pcm."
 
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