Error code 31 and severe lack of power

Hey guys,

I have a GTO TT 1992
unfortunatly I do not have a logger due to me not being able to find one here in the UK

I have an issue where my car is massivly down on power and using a test light on the diagnostic port i get error code 31 (3 long and a short) for knock sensor.

I did some reading of old threads on here and many suggested a bad harness or sensor.

Where my problem differs is that i have checked my harness and confirmed no shorts and good connection to the ECU but when iu unplug my knock sensor the car drives (with the same lack of power) but when i get into mid rpm the check engine comes on again for error code 31…even though its not connected!

how can the engine detect the same knock when the system is connected or disconnected?

Also is there a “proper” test proceadure i can do to verify the knock sensor & output from ECU please?

check out the manuals section here for your year … the file should contain how to test or diagnose individual sensors

Hi is there any obd 1 diagnostic code reader for our gto?

Yep approx $200 from Blackstealth would be a good place to start. Please research this thread before deciding obd1/obd2 reader

You could also try this page error 31 points to Harness/connector/detonation sensor

obd1 codes Jeff Lucius knows his stuff

knock sensor ? If you have a service manual. Its Page 13A-27.

Thanks all, so after more digging it would appear my knock sensor has no continuity and supply’s no voltage woth the hammer test so I think it’s a dead knock sensor

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Your best bet is to replace that sensor, but I can help you with the datalogger, I build one using the DSM cable and it works fine with my 91TT, if those use the same OBD1 protocol then you can log your the same way as the USDM,
I put together this wiki page:

You need the FTDI serial to USB adapter (it should be available there), you can use one with a different connector just make the appropriate pin connections.

I remember having a bad knock sensor, when knock was detected the car was sluggish and you could tell by the logs after a knock count there was a timing change.

Tha k you for thst, I did replace sensor and it solved the issue, now I have some other issues so I can build the data logger you posted about :slight_smile: thank you