I read the diagnostic codes and got 1-4-3 in socket 6 and 2-3-2 in socket 2. I replaced the knock sensor and erased the codes but it returned. I checked the voltage at the knock sensor wires and it read zero. What unit sends that voltage to the knock sensor and where is it located. As for code 2-3-2, the car runs fine except for a rough idle. I've removed and cleaned the throttle body and the idle air motor. I've also had the injectors cleaned and there is no fuel pressure loss, so the injectors are not leaking. What else could be causing this? This forum has been a great help and I want to thank those who share their valuable knowledge with us.

 

Me I would start with the 232 code that means you have a vaccum leak somewhere making the computer adjust the fuel system to compensate.

That might be disabling the Knock sensor signal.

I would check and repair all vaccum leaks clear the codes and see what happens.

 

A 1-4-3 code is a knock sensor self-test code. My Volvo has been setting that code for many years (I have receipts from the P.O. to prove it). Every once in a while I work on it, but have not found anything definitive. Except that previous technicians have travelled the same roads as me already (evidence of voltage tests and socket backprobing abound).


There are discussions of this problem on the Brickboard FAQs

You can't easily measure the sensor output, its a tiny voltage. The self-test signal that generates the 1-4-3 comes from the ECU (in the right side kickpanel).

Doesn't the ECU switch to full retard of ignition timing when the 1-4-3 is set? That's the reason I always reset the code ASAP.

 

im guessing this is the turbo 940 you guys are talking about since it has a knock sensor. do the n/a's have a knock sensor as well? my car is not quick but i didnt think anything of it but it may have the same problem although i dont have a check engine light right now.

do you guys use a paperclip to jump pins and flash the error codes or do you have to use a reader for the volvo's.

 

Yes the N/A have knock sensors.

If it is a newer car and you have OBDII then you need a scanner If you have OBDI follow link.

http://www.troublecodes.net/Volvo/

 

The car in question is a '93 940 so it has OBD 1. That Link (above) gets you to the code list and reset instructions. But it doesn't go into the Why of the codes' setting. The Brickboard FAQs do.

Aside from a bad sensor, the cause could either be wiring or the torque on the sensor mounting bolt...they have to be tightened correctly to work right.