Engine light on. Codes 2c9c and 2c61

Xtony · #1 02-04-2013, 09:50 PM

2008 X5 4.8 with 70 k miles. Reset the codes but engine light back on. North codes appear to have something to do with "lambda probe front catalyst". Has anyone dealt with these codes? Should I replace the pre cat O2 sensors and go from there?

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ard · #2 02-07-2013, 12:14 PM

Sorry, missed this...

You have two simultaneous codes, one for each O2 sensor?

It is unusual for two parts to fail simultaneously... two possiblke causes:

1. A wire got damaged underneath;
2. the fuse to the sensors is damaged.

If you are gettig a "pre-heat circuit" failure, then this is NOT related to their 'function'...when the car starts up, immediately power is delivered to the sensors to warm them up- this is different that the sensing function (this is why there are 4 wires to each). Look at the wiring diagram, see of there is a common fuse (on other BMWs there IS and it is NOT in the fuse box (!!!!)). Or look at the common connector underneath for damage.

GL

A

Xtony · #3 02-07-2013, 01:02 PM

I looked at the connector box and replugged the passenger side front sensor in. Everything looked fine. Cleared the codes but they came back a few miles later. I think both codes are for bank one, pre-cat sensor. I think I'm going to try to replace that sensor. Looks like it will be a pain to get access to it. Can't get to it from above like most pre-cat sensors, but it's also hard to reach from below, even with all the covers removed.

95wildtt · #4 02-07-2013, 07:46 PM

Have you replaced the battery, yet?
Lots of weirdness from an old battery... Just replaced mine last fall.

Xtony · #5 02-07-2013, 09:59 PM

Quote:

Originally Posted by 95wildtt

Have you replaced the battery, yet?
Lots of weirdness from an old battery... Just replaced mine last fall.

Battery and alternator were replaced about a month ago. Battery seems strong. Don't think that's an issue and the code stamps show 14 volts at the time the faults triggered.

Xtony · #6 02-08-2013, 02:46 PM

Quote:

Originally Posted by ard

Sorry, missed this...

You have two simultaneous codes, one for each O2 sensor?

It is unusual for two parts to fail simultaneously... two possiblke causes:

1. A wire got damaged underneath;
2. the fuse to the sensors is damaged.

If you are gettig a "pre-heat circuit" failure, then this is NOT related to their 'function'...when the car starts up, immediately power is delivered to the sensors to warm them up- this is different that the sensing function (this is why there are 4 wires to each). Look at the wiring diagram, see of there is a common fuse (on other BMWs there IS and it is NOT in the fuse box (!!!!)). Or look at the common connector underneath for damage.

GL

A

Ard, would you happen to know where the fuse(s) to the O2 sensors are on the X5 4.8? I know that on some other BMWs they are under a cover in the engine compartment with the DME. Before contorting myself to replace the pre-cat sensor, I want to take a look at the fuse. All the wiring I can follow seems intact.

BTW, the actual codes are for Lambda probe heater front catalyst, control and Lambda probe front catalyst, electrical error.

ard · #7 02-09-2013, 01:23 AM

I do not. Saw your other post.

Do you have access to the schematic? It should tell you the fuse, and location

Xtony · #8 02-09-2013, 09:33 AM

The WDS shows it with the fuses under the glovebox, but it's not very clear. I checked all of the fuses there, and they were fine. I'm going to go ahead and swap the sensor today.

ard · #9 02-09-2013, 02:38 PM

Quote:

Originally Posted by Xtony

The WDS shows it with the fuses under the glovebox, but it's not very clear. I checked all of the fuses there, and they were fine. I'm going to go ahead and swap the sensor today.

Wait- there should be a power and ground to the sensor that powers the heater circuit- and a separate pair for the sensor itself. (4 wires) You should figure out which two are the heater, and pop a voltmeter onto the connector to see if it is being powered- if not, then you know the sensor wont fix it.

Then again, a new O2 sensor is always nice to have!

GL
A

Xtony · #10 02-10-2013, 10:03 AM

Ok, so I replaced the pre-cat sensor on bank 1 (passenger side) and drove around fifty miles yesterday without the engine light coming back on. I'll update after some more miles. The sensor wiring looked intact under the sheath so I guess it might have been a short or interruption inside the sensor itself.

As for replacing the sensor, what a pain! Definitely a two person job. I had to attach my crowsfoot sensor socket with two universal attachments and several extensions all duct taped together. I then pulled the sensor cable ( it's around three ft long) up near the passenger side firewall so I could feed the crowfoot down from above. I found it helpful to tape the slit on the crowfoot tool closed so it wouldn't fall out on the way down. Then I slid it down the cable as someone below the car helped it into place and held it while the other person loosened the sensor with a breaker bar. Once it was loose, I was able to spin it of with two fingers from below and the new one went in fairly easily. Now I know why the dealers charge big bucks for that job! Whose idea was it to put those pre-cat sensors there?

Edit: Been a couple of days and a 100+ miles and no engine light!!!!

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