Repetitive Knock Sensor Code - '94 850 T5

pdemol · Post by **pdemol** » 26 Mar 2011, 01:32

G'day Everyone,

I have been pulling code: 1-4-3 from socket A2 on my volvo 850 T5 on and off for the last few years.
When It first came up I replaced the knock sensors with the updated ones from groton.
Code went away for a while but returned again a few months later. I cleared the code and it was ok for a while only to
come up again after a while.
I've tried swapping the sensors around a few times with no real change. They are torqued up and orientated correctly.
Spark plugs are only ~30k old. Haven't changed the PVC since I bought the car (180k ago) but no smoke coming up oil dipstick when engine idling. I'm using 95 octane fuel.
I've checked all the forums here for help but cant seem to solve the problem. The car has no other problems and drives beautifully when not showing this code.

Any help would be really appreciated.

Many Thanks.

Post by **jimmy57** » 26 Mar 2011, 08:52

There is a known issue with this. The knock sensors with connectors directly on knock sensor will vibrate enough to wear the trerminals. Called "fretting". The fix is a kit with new knock sensors with wire leads made on and the connectors to engine harness are remote.
You may get a fix by using a pick and pushing the sides of terminals in harness connector together so they are tighter on knock sensor pins.

pdemol · Post by **pdemol** » 26 Mar 2011, 20:53

Thanks Jimmy57

However, don't think that is the problem with my knock sensors as I have installed the updated ones from Groton. There is no connector on the actual sensor with these ones. The wires (with protective plastic sleeve) come directly out of the sensor.

Any other ideas?

Post by **jimmy57** » 26 Mar 2011, 22:10

the connectors on harness still can be the problem. I have had to replace the terminals when installing the updated knock sensors to get the problem resolved if the terminals were worn badly.

pdemol · Post by **pdemol** » 27 Mar 2011, 17:23

Ok. Sounds like its worth a try. I'll pull off the manifold and check all the connectors again.
Thanks Jimmy57.

easyvolvo850 · Post by **easyvolvo850** » 02 Dec 2011, 07:34

Hi pdemol. Did you ever get this figured out? I am having the same issue with my 94 850 turbo wagon. I have put in new plugs, new plug wires, cleaned the TB, regreased the connectors and am still getting the 143 code about three days after I reset the computer. Its getting very annoying. I have the new style of knock sensors too where the connectors are further down the wires. HELP..

Post by **rspi** » 02 Dec 2011, 09:10

What octane are you pumping? I didn't think this would be an issue if you used 91+ octane???

easyvolvo850 · Post by **easyvolvo850** » 02 Dec 2011, 14:25

I run at least 92 all the time.

claymore850 · Post by **claymore850** » 10 Dec 2011, 22:11

Take a look on some metal part knocking the engine while drives. Sometimes this kind of vibration can be detected as knock.

Also check your fuel octane, make a compression test, to avoid engine related problems, my 850 turbo starts a few months ago with the same problems, until i check the compression. (i found between 125 and 75 psi..nearly dead engine). That's the source of vibration inside the engine. The carbon buildup over the piston heads can make a hot spot inside, who lets the gasoline burns before the TDC.

donis222 · Post by **donis222** » 20 Nov 2013, 13:01

To the best of my knowledge, one can diagnose the knock possibility if you have a live data scanner, code reader. Watch the timing when the code sets. If you aren't under heavy throttle and the engine is cool and the code sets, then the problem is the sensor or wiring.

If the code sets only under heavy throttle then the problem is knocking. Watch the timing it should advance until very heavy throttle then back off.
Causes: low octane, carbon in combustion chamber (rare these days), or bad computer (highly doubtful).