MOT - engine management light - does it have to be visible?

[thetapeworm]

I'm trying to troubleshoot a current problem, 4 sensors replaced so far, each one clearing a specific code apart from one lambda sensor. I've tried two now and the light still comes on. In the meantime the MOT has run out but I could do with be able to use the car.

If you take a vehicle for an MOT and the tester is unable to see an engine management light that's lit, say it's obscured by a sticker or similar, is that an issue apart from being totally council and shameful?

Just trying to think of a temporary work around until I get it sorted.

[thetapeworm]

Cheers, I thought they'd have this covered but thought I'd ask, best dust off my push bike!

[thetapeworm]

He bulb can't be taken out, it's on the circuit board buried inside the sealed dial unit. Of course it could be broken down and damaged but I'm not doing that.

steve-5snwi said:

Whats the fault codes you have & make and model ?

It's an '02 petrol CRV...



I've replaced both lambda sensors, number 1 twice, and also the knock sensor as that was throwing a code too.

Codes only came up once I decided to sell it 😂

[thetapeworm]

SS2. said:

The fault log is reporting higher than expected voltage from the heated O2 sensor.

It might be worth clearing the fault codes and disconnecting the affected sensor. If the fault remains high voltage, the problem is between the sensor plug and the ECU. If the fault changes tor low voltage, the problem is most likely to be the sensor itself.

steve-5snwi said:

If you clear the codes and the light goes off how long does the light stay off for ? if its 10 miles or so book the car in for an MOT, clear it in the carpark and prey it doesn't come on while being tested.

If you disconnect the sensor does the code change ?

At the moment the light comes back on as the car starts to come up to temp. I can't drive it anywhere so am restricted to idling on the drive, it appeared after about 10 minutes.

I really don't do electrical stuff so hadn't fully understood the nature of the fault, hence me changing the sensor twice (the first was a cheap Chinese one so I presumed it was rubbish, the second a Bosch one). It's not a car that's worth much so I'm trying to save where I can as I need the money from the sale to get my Saab back on the road.

Based on your much appreciated replies I'll try things disconnected and also pay more attention to the sensor readings from Torque when it's connected to the reader.

Cheers!

Edited by thetapeworm on Wednesday 26th December 19:39

[thetapeworm]

red_slr said:

What condition is the plug in? That's the first bit I would be looking at.

I didn't pay a huge amount of attention to be honest but when I unplug to test further I'll give it a clean - it's quite exposed.

Edited by thetapeworm on Wednesday 26th December 20:50

[thetapeworm]

TooLateForAName said:

Just want to make sure that this useful post isnt lost in the arguments over mot rules...

It was very much noted by me

[thetapeworm]

I'm going to admit defeat and book it in, had a bit of a look this morning and found this with the sensor unplugged...



Plugged back in and cleared codes, sensor voltage looks like this:





Then when I rev the engine:



Then, after a while, it jumps to a constant 1.3v and the engine warning light comes in.



Error:

[thetapeworm]

steve-5snwi said:

Have you removed the CAT to see if its broken up ?

I haven't, I'll probably have to leave that to the garage as it's been on there a while and I'm likely to struggle if I snap any bolts.