Hi,
The Check engine light on my '95 E420 keeps returning. I get a Code 2 which seems to show a problem with the temp sensor. The indicated temp has always been normal and seems to be operating correctly. I reset the Code and it returns after the engine has been shut off. I live in a very hot area and the indicated temp climbs while the engine is off.
Should I replace the temp sensor? Any ideas?
Anziani

Where did you get that code from????????

Andy,
I got it from the flashing led's after holding the switch down for 4 seconds.
Anziani

No Andy here , but that;s OK..

Code 2 temp sensor would be an engine management code. Not a DM/CE code.

What I meant to ask is where did you find code 2 to be listed as a temp sensor code??
My info states a code 2 from the DM to be a bad 02 sensor heater circuit fault.

Arthur,
Excuse the "andy".
My mechanic looked it up on his repair CD. Could he be wrong?
Anziani

Arthur,
What I meant to say was that I got two led flashes and the mechanic said that that meant a problem with the temp sensor.
Anziani

I think he may be mistaken.. code 2 from the LH/SFI module would be a temp sensor code, but a code 2 from the Diagnostic module [ meaning the CE lamp activator emmissions module that has the button/led under the hood] indicates you have a heater circuit malfunction at the 02 sensor..and that would certainly turn on the CE lamp, right quick.

The leads are under the passengers side rug and the heater circuit is the two white wires..try some test there [ specially an OHMS reading]

Again, did the flashes come from the sw/led under the hood or did he get those codes with a code tool from the LH module ???????
It is all togeter possible that he did in fact get a sensor code from the ECU and you think he got it from the built-in led.., so , that is the question..

Arthur,
He got it from the led/sw under the hood and cleared it. When it happened agian, I checked it myself, reset it and then later on it came back. Definitely the led mode and two flashes.
Thanks for your help.
Neil Mahony

OK ...
That being the DM, my charts say you have an 02 sensor heater problem.

Arthur,
Thank you so much for your help. We have a new O2 sensor but had not installed it yet. Lucky coincidence. Will install next week.
Neil Mahony

Good ..
Just be aware of the fact that a 02 heater code does not mean you have a bad sensor.. it means the DM computer is not seeing a current draw of proper specifications..which could be anything in that circuit , from a bad heater in the sensor, no power to connector, etc..
You may want to do an ohms test on the new one and compare it to the old for heater ohms verification [ along with a ground test]