Lambda sensor?

[andymadmak]

Evening all!

I have a little project car I am working on - a 2003 Rover 25 1.1 16v. It had a head gasket failure 2 years ago that was properly repaired with a head saver gasket thingy ( technical expression! ) new pump etc, and it runs peachy fine. ( I am always amazed by just how refined and sophisticated the little 1.1 engine feels)

BUT, since the replacement, the orange engine light has been on. At the time the garage that did the HG replacement said that it was probably a lambda sensor but the then owner said he did not want to spend any more and just ran the car with the light on ( for two years! )
Now the car is mine and I want to get it fixed up properly. It runs very well indeed.......although every once in a while it simply has no power. Idles fine, runs fine, just will not pull at all. No missfires, no hiccups, just gutless. A quick restart restores the power. So, I put my OBD2 reader on it today and it came back with error code 135, heater sensor bank 1.

Is this the pre cat lambda sensor failure code? No other codes logged and all oils, fluids, temperatures are all good.

I hope someone can confirm its the pre cat sensor.... Looking at it, it looks like a straightforward change! ( cue someone telling me I am in lala land with my thinking! )

[andymadmak]

A little extra information.

I have checked the oxygen sensor fuse in the engine bay fuse box and it is OK. I can reset the engine light with my OBD 2 reader, but it only stays off for a couple of miles before coming back on with the same 135 code.

[Mr2Mike]

Easy enough to check, just unplug the oxygen sensor(s) and measure the heater resistance with a multimeter (white wires normally on a four wire sensor). Typically the resistance will be under 10 ohms on a good, cold sensor. The resistance increases with temperature, which is how the sensor regulates it's temperature.

If the sensors check out ok, then it's probably a wiring fault i.e. a broken wire, corroded connector or possibly a duff relay etc. If you can back-probe the connector(s), check you are getting 12+v with the engine running.

[jith]

andymadmak said:

Evening all!

I have a little project car I am working on - a 2003 Rover 25 1.1 16v. It had a head gasket failure 2 years ago that was properly repaired with a head saver gasket thingy ( technical expression! ) new pump etc, and it runs peachy fine. ( I am always amazed by just how refined and sophisticated the little 1.1 engine feels)

BUT, since the replacement, the orange engine light has been on. At the time the garage that did the HG replacement said that it was probably a lambda sensor but the then owner said he did not want to spend any more and just ran the car with the light on ( for two years! )
Now the car is mine and I want to get it fixed up properly. It runs very well indeed.......although every once in a while it simply has no power. Idles fine, runs fine, just will not pull at all. No missfires, no hiccups, just gutless. A quick restart restores the power. So, I put my OBD2 reader on it today and it came back with error code 135, heater sensor bank 1.

Is this the pre cat lambda sensor failure code? No other codes logged and all oils, fluids, temperatures are all good.

I hope someone can confirm its the pre cat sensor.... Looking at it, it looks like a straightforward change! ( cue someone telling me I am in lala land with my thinking! )

Upstream lambda sensors almost never survive a head gasket failure. The high temperature water vapour passing over them kills the heater and most times the oxygen sensor.

I don't know how the previous owner managed to run it for 2 years like that as it is an MOT failure. It's really not worth scrimping on for all it costs.

J