Knock Sensor Problem

[VZRacing]

We are getting a “knock sensor circuit malfunction” DTC.

We have tested the knock sensor wiring on the harness side- it tested fine. We have replaced the knock sensor itself with a new one (twice). We have tried grounding the knock sensor in many different ways.
Dsmlink v3 shows that with any significant throttle input (2% and over), the ecu pulls 3 degrees of timing. It always pulls 3 degrees and never pulls more than 3.
I’m guessing this is a safety measure given the knock sensor malfunction. We even ran a wire directly from the knock sensor to ECU pin 9 (detonation sensor) with still no results.

Does anyone have any suggestions on how to fix this knock sensor problem?

 

[cougarelimin8or]

Do you have the knock sensor mounted in the stock position?

 

[VZRacing]

Yep right on the back of the motor, under the intake manifold.

 

[radix]

faulty cable? Can you do you knock or see an error without dsmlink hooked up?

 

[cougarelimin8or]

With link hooked up, can you create a knock and have it register on the screen?

 

[VZRacing]

With link hooked up, can you create a knock and have it register on the screen?

I have tired simulating a knock as described in the Haynes manual by "tapping/hitting" the block with a hammer to see if the sensor picks anything up; DSMLink did not register anything. I also took the sesnor out, grounded it, and then hit it against the strut housing, with the same result.... nothing

 

[VZRacing]

faulty cable? Can you do you knock or see an error without dsmlink hooked up?

When DSMLink isn't hooked up the check engine light stays on. I don't think the cable on the sensor is bad since I have gone through 2. The wiring harness may be bad but I don't see how. One terminal read 8v exactly (Haynes manual says it should be between 8 and 11v), and the other terminal should go to pin 9 on the ecu. I ran a new wire directly from the knock sensor to ecu pin 9 and it's still throwing a code.

 

[VZRacing]

Another interesting thing.... the car throws the CEL when the engine isn't running; as in the car turned to the "ON" position.

 

[VZRacing]

As it turns out the problem was not our car! Apparently there was a problem with all ECU's the guys over at DSMLink sold this year for the 1990's. There is a resistor that needed to be installed to "pull-up" the knock sensor pin. After that was soldered in place everything started working properly!

They just put up a post today about the issue, if you are having a problem and bought an ECU for a 1990 from them recently you might want to drop them an email.

Their post:
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If you ordered a 1990 EPROM ECU from us since December 2008 or you sent us a 1990 non-EPROM ECU for the EPROM conversion, please be aware that we have identified a compatibility issue in these ECUs related to the knock sensor circuitry. If you have one of these ECUs and are currently getting a knock sensor error, please contact us offline to arrange for a free fix.

twdorris at ecmtuning.com

I've already sent out e-mail to everyone I could find in our order database. But just in case I missed some, I wanted to post it here too.

Thanks and sorry for the inconvenience,

Thomas Dorris
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Thanks to everyone who tried the help.