Lambda Sensor

[Citroenfan]

Have a problem with our 92 XM, that so far has resisted any attempt at finding a solution.

It all started about 5 months ago when I had to replace a faulty catalytic convertor. In the process of removing the defective unit, the shop accidentally damaged the lambda sensor. They replaced it with a Bosch unit - basically the same one that got damaged. The problem is that the Bosch unit does not have the Cit specific connectors on the wire loom end so the original (done long before we acquired the car) was spliced into the existing wire loom in the car - at the sensor end. Now the shop swears up and down that they did the new one exactly the same way. However, now the check engine light comes on after a few blocks of driving. However, engine performance and mileage have not been effected - I do keep accurate notes about that.

My understanding on the 02 sensors with the pre-heater installed is that the heater circuit should show about 3 to 5 ohms resistance and the sensor wires should show, basically,an infinite reading. When I check the wiring on the car it looked as though the wires were reversed. IOW the plug with the infinite reading was plugged into the plug that shows +12.8 volts (ignition 'on') and the two wires showing approx. 3.9 ohms were plugged into the other receptacle. Prior to doing anything I pulled the codes out of the computer (12 valve V6 engine installed) and got the following errors

13 - "injection air temp sensor"

36 - "Relais oxygen/lambda sensor heater"

52 - Air/Fuel mixture control loop

Soooo - taking my heart in my hands I switched the plugs, putting the 'heater' circuit into the 'hot' receptacle and the 'sensor' circuit into the other receptacle.

Car would not start. Period. Switched the two plugs back to their original positions - Car would not start. Fearing I had blow something I just sat down and silently yelled at myself. But figuring, what the heck - disconnect the ground wire from the battery and left the car overnight. Reconnected the battery the next morning and the damn thing fired right up as though nothing was wrong. Do keep in mind that the lambda sensor wires were still in their 'original' positions. Drove the car for a couple of days - all seems normal.

Yesterday decided, just for kicks - to pull codes again. Got absolutely nothing with the reader. IOW did not even get the start code of '12'. Tried a couple of times with the same results. Tried starting the car - would not fire. Disconnected the battery, again, and let the car sit for about 20 minutes. Reconnected the battery - car fired right up. However, now when I check the lambda sensor plug that should have 12 volts on it - get nothing. Engine runs just fine, plenty of power and idles smoothy.

So my basic question - what have I screwed up and how badly . Any and all ideas are more than welcome.

Regards,

Steve Hammond - lonely in Los Angeles with an XM (only about 50 were brought into NA in the 90's via Andre Pol and not real sure how many are left )

July 26th - UPDATE

On the advice of a good friend (and CX owner who works for a local auto repair facility) I double check the power connection plug for the O2 sensor - it was bad (broken internal connection). Hein was kind enough to give me a new connector (Bosch I believe). Sliced the new connector (soldier and heat shrink) into the power leads and hooked all back up. Car fired right up - engine light came on again after about 45 seconds of running. Just has it had in the start of all of this BS when the new Cat was installed and the shop damaged the original 02 sensor. However this time when I pulled codes I got the following: 13 and 52.

According to the info I have 13 is for the 'injection air temp sensor' and 52 is 'Air/fuel mixture loop'. Though the check section of the info sheet says that this may be the result of an 'inlet or outlet manifold leak' have a bit of a hard time seeing that as nothing there was touched. However I did double check the resistance reading of the currently installed sensor - the sensor circuit shows 4.8 ohm. I had gotten a new sensor specific for the XM and Peugeot 605. The sensor circuit on this unit only shows 2.8 ohms resistance. So am going to install and see if things go back to normal - or as normal for an XM as it could be

I think that the 13 code may just be the result of a tarnished connector pins as that sensor is basically brand new (less than 2 years old).

Steve

This post has been edited by Citroenfan on July 26, 2016 05:40 pm

[Citroenfan]

Update - though a bit late . Got a sensor from Europe that was specified as specific for my model XM. Installed and light now goes off as it should. A real conundrum, however as the unit that had been installed, and not working - at least according to the on board computer - was the same cat number as the one that had gotten cut through during the cat convertor replacement and replaced.

Steve