help with knock sensor 98 7.4L

[Charofire]

I've been chasing my tail on a truck I purchased last summer to ultimately give to my father. It's a 1998 gmc Sierra 2500 with a 7.4L. After having the tranny and tCase resealed, the transmission shop owner said that the PCM was never sending a signal to the torque converter to lock up. He said he didn't know why and didn't want to recommend replacing a bunch of things without knowing more. I purchased a rebuild PCM. Still no signal was sent to the TC to command lock up. So, I finally found a pending code. p0327. No KS activity, low voltage -sensor 1. I replaced the knock sensor and tested the wiring for continuity. Still has the same trouble code after replacement. What was strange was no coolant poured out of the side of block when I removed the old knock sensor, and the coolant level shows full and I've driven it 300 miles in the last two weeks. Could a blockage be the cause of malfunctioning knock sensor?

 

[Erik the Awful]

Not likely. The knock sensor is a piezoelectric element. It senses shocks. On most vehicles it isn't plugged into a coolant port. The coolant port on our engines just happens to be a handy place.

 

[BeXtreme]

The knock sensors on my 97 don't go into coolant ports. They are blind holes. You also have two knock sensors, one on each side... did you check both of them? Your wording makes it sound like you only checked and replaced one.

 

[Charofire]

Correct, my scanner showed only bank 1 being the problem, so I replaced the drive side knock sensor.

 

[BeXtreme]

How did you test them? Check for continuity from the wire back to the pin on the ECU? Checked for short to ground on same wire? Checked for resistance in the sensor? You can also put the new sensor in a vise and put a multimeter on the sensor and whack the vise with a hammer. Here's a good video.. these are the same sensors used on the L29.

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[Schurkey]

Small-blocks thread the knock sensor into the block-drain port just ahead of the starter. Vortec big-blocks thread 'em into blind holes as said. I don't know about TBI big-blocks. Probably the same as Vortecs.

Did you check the wire harness for the knock sensor?

WHAT ARE YOUR MISFIRE COUNTS FOR EACH CYLINDER? The computer will disable the torque converter clutch if it senses misfire.

 

[Erik the Awful]

Doh! I always forget that there are big blocks out there.