OK, so I just got the codes pulled at the local McParts store on my 850 Turbo. The codes that came up Im sure look familiar to some of you guys from what Ive been reading up on. I understand that P0331 and P0326 are for each of the knock sensors on the front of the block. Also I have read that there was an old style that had one harness for both sensors and a new style that had individual plugs for each knock sensor. I am assuming that I have the old style and no one has switched to the new style.

That is where I have some questions.

1. I have been cheap and have been filling up with 89 octane instead of 93 octane. I think I already know the answer to this but, do these cars require 93 as per manufacture's specification? : puts on flame suit :

2. Could this have set of DTC's for both knock sensors?

3. I am going to try cleaning the connections and inspect the wiring then clear the DTCs, and see if the CEL comes on again. If I do have to buy new knock sensors and the connectors for the new style, where do you guys suggest I purchase them from. I do have a buddy that gets parts for me cheap from Worldpac thru the Mercedes service center but does Worldpac supply the newer style knock sensors and connectors?

Thanks for your help guys.

 

Theoretically you should be able to run 89 octane w/o problems but you're not going to get peak performance or mileage, and by doing so you're making the knock sensors work overtime!

What I would do is reset the CEL; put decent gas in it (91 or better octane) and see if the codes come back.

If they do, here are the diags from the manual:
================================================== =========
Code 1-4-3 (Front Knock Sensor Signal) &
Code 4-3-3 (Rear Knock Sensor Signal)
1) If fault is intermittent, check camshaft setting. See the
2.3L article in the ENGINES section. If camshaft setting is okay,
check all wiring and connectors for poor contact. If fault is
permanent, go to next step.
2) Turn ignition off. Check camshaft setting in relation to
crankshaft. Repair as necessary. If camshaft setting is okay, gain
access to knock sensor(s) by removing upper charge air cooler pipe and
engine cooling fan. To gain access to rear knock sensor also remove
intake manifold support bracket.
3) Ensure ignition is still off. Wait 2 minutes. Disconnect
knock sensor. Connect an ohmmeter between knock sensor connector
terminal No. 2 and ground. If ohmmeter reads about zero ohms, go to
step 5). If ohmmeter does not read about zero ohms, go to next step.
4) Ensure ignition is still off and knock sensor is
disconnected. Ensure ECM connector is making good electrical contact
and is connected securely to ECM. Connect an ohmmeter between knock
sensor connector terminal No. 2 and ground. If ohmmeter reads about
zero ohms, code was caused by poor contact in ECM connector. If
ohmmeter does not read about zero ohms, check wiring between knock
sensor connector terminal No. 2 and ECM connector terminal A17 for an
open circuit.
5) Ensure ignition is still off and knock sensor is
disconnected. Connect an ohmmeter between knock sensor connector
terminal No. 1 and ground. If ohmmeter reads about zero ohms, check
wiring between knock sensor connector terminal No. 1 and ECM connector
terminal A2 (Code 1-4-3) or terminal A30 (4-3-3) for short to ground.
If ohmmeter reads about one megohm, go to step 7). If ohmmeter reads
infinite resistance, go to next step.
6) Ensure ignition is still off and knock sensor is
disconnected. Ensure ECM connector terminals are free of resistance
and oxidation. Reconnect ECM. Connect an ohmmeter between knock sensor
connector terminal No. 1 and ground. If ohmmeter reads about one
megohm, code is caused by poor contact in ECM’s connector. If ohmmeter
does not read about one megohm, check wiring between knock sensor
connector terminal No. 1 and ECM terminal A2 (Code 1-4-3) or terminal
A30 (Code 4-3-3) for an open circuit.
7) Reconnect knock sensor(s). Start and warm up engine.
Increase engine speed to slightly greater than 3500 RPM. Use Volvo
Scan Tool (998-8686) to check knock sensor value. If knock sensor
value is 2-6 at speeds greater than 3500 RPM, source of code is poor
contact at knock sensor connector. If knock sensor value is not 2-6 at
speeds greater than 3500 RPM, test system using a new knock sensor.
================================================== ===

Sorry, can't help you w/WorldPac; never heard of them...

 

Awesome, thanks for the post. Ive got to get my own OBDII reader/scanner so I can delete the codes. As far as the parts, if I need to get them I will probably just get them from IPD. I just noticed last night after I posted this, that IPD sells both types