After a few failed attempts to prevent the Check Engine Light (CEL) from turning on, I have put the car back on the road and am trying again. This time it took about 75 miles to set the code. It would be nice to sort it out before taking the 2500-mile trip to Maine and back. I’m getting codes 231 and 221 in Socket 2 of my EGR equipped non-turbo 95 945. I believe this is a Bosch 2.4 with EZK ignition. It is defiantly not Rex-Regina.

I am not having any drivability, idling, starting, or stalling problems. I have already made several repairs for air leaks, or imminent air leaks, and I installed a new air filter.

I do seem to have a bit of “tip in” hesitation from a dead stop, but the Throttle Position Switch (TPS) passes the OBD check, and I have heard the switch click when moving the throttle off of the idle position. I also think I am not getting the fuel mileage that I should get. I haven’t put many miles on the car, but it seems I get 20 – 21 with local driving, and on one 300-mile highway trip I only got about 22.

Table 1 in the FAQs for interpreting the OBD results indicates similar problems for both 231 and 221, but part of the explanations are confusing me. Does the bracket in the “Causes or Fault” column for fault code 231 mean that the Cause or Fault is continued in the explanation for fault code 232, which also has a bracket. In other words, I see that fault 231 can be too lean or rich, but the fault explanation is only for being too lean unless you read the explanation for code 232, which describes a too rich fault.

I see that low fuel pressure can be a cause for these faults. The Fuel Pressure Regulator (FPR) looks like it may have been replace recently, and the hose does not smell of fuel. Is there a test that I can perform on this with a Mighty-Vac beyond checking for a ruptured diaphragm? I don’t currently have the gear to test the fuel pressure, but I suppose I can make it up if need be.

When I did the OBD test 3, I did not hear a response from the Radio Suppression Relay (RSR), but I am not sure of its location. I think it is on the right fender well, and I also thought the car would not start without it. I heard no response from the cold start valve, but I think this car is not equipped with one. I heard no response from the carbon filter solenoid, but I don’t know if I have that either.

It seems that Table 1 only indicates an O2 sensor problem for code 231 if you have the Motronic 1.8 system, which I don’t think I have. However, I know cause and effect problems can bleed over. I’ve seen the instructions and discussions several times regarding the voltage check of the O2 sensor. However, I have never been able to figure out if the check is done with it disconnected, or if I need to intercept the wires and check it while it is connected. So, which way is the correct test for the O2 sensor?

Any suggestions are welcome. I don’t have a spare 016 AMM to try. I have cleaned it with AMM cleaner, which seemed to make no difference. I hope to get to the junkyard sometime to look for a spare.

Thanks,
Charley