Crank position sensor code

[spark3542]

I'm running a 97 K2500 Suburban on homebrew biodiesel.

I getting a lot of bizarre codes and need some advice.

The most frequent code is Crank Position Sensor ckt malfunction. I reset the code, and the truck runs nice. The biodiesel runs very quiet, then up on the highway I will get loud diesel knocking sound and the code is set again. The loud diesel knocking will come and go very abruptly, but no loss of power or change in "feel"

On every other startup of the engine, it will be hard-starting, and also start in this "mode" where the revs will not exceed 2k, and it has very poor acceleration. When it does this, I shut off the motor and restart. It restarts immediately and drives fine.

Other codes also show up...Turbo boost sensor "A", Inj timing circuit, even occasionally the P0606 ECM code. Most frequent, however, is the Crank Position sensor code.

I looked at the passthru on the firewall where the ECM wires are, and they were rubbing against the metal AC lines, to the point where one yellow wire was worn through to the copper. It may have shorted, but it doesn't seem like it's broken. I installed some foam to keep the wires away from the AC lines. Still getting the codes and the bizarre "no acceleration" startup mode.

Anyone have any insight?

Also, where is the Crank Position sensor located so I can troubleshoot the sensor?

Thanks

Mark in MA

[john8662]

First and foremost just check all the electrical connections on the back of the firewall that are behind the fuel filter housing, anything loose here and you'll get problems.

Second, it's likely that the crank position sensor is bad considering the symptoms you're getting. The idea here is to eliminate codes starting with the beginning code. Check the connection to the crank position sensor, it will be slightly to the right (on the driver's side) of the injection pump kinda buried slighly underneath the thermostat crossover pipe.

The crank position sensor is located in the timing cover, also on the driver's side. I believe underneat the the power steering pump on that year model. It's toward the bottom of the cover, near the crank. They are pretty difficult to actually get out of the hole. But some patience and rotating it some helps greatly.

[spark3542]

I didn't have much time last night, but I did pop the hood to located the wiring, saw the connector under the thermostat pipe, and the wire running past the PS pump. Does the sensor body just screw in...similar to a temp sender?

Thanks

Mark

[john8662]

It doesn't screw in, it's pushed in place and held in by a plate and retainer bolt (13mm head), rotating it helps it free it, otherwise prying it with a screwdriver on the plate or pulling on the wire results in a the plate breaking off and the wire breaking too, then the fun begins.

J

[spark3542]

Good news:
Crank Position sensor is fairly easy to get to...turn the steering wheel to the left all the way to move the tie rod out of the way and the ckp is easy to get at, one bolt, and work it free by hand.

Bad news:
CKP sensor is about 3" long and you can get it almost out before it hits the case of the PS pump. To get it out, you must remove the belt, loosen all PS pump bolts and swing the pump out of the way...what a pain.

Bad News:
I still get the crank position sensor circuit malfunction code after erasing the code twice and taking several trips. I guess it's time to ring out some wires.

Mark in MA

[rjwest]

Knocking sound :

I think you are starving for fuel ( IE: same as running out of fuel ) that would correlate with GM manuel on codes being set for " running out of fuel """

Also, There is a 'Blurb' in the manual about " key'
faliure or loose harmonic balancer, Should see missed
counts on the optic sensor for this,,