Oxygen sensor fault codes again - 1.8

[EVS]

Hi all
I've got the check engine light come on once again.
This time it reads the following codes:

• P1191 - Oxygen sensor heater open circuit, downstream sensors

• P0445 - Evaporative emission control system purge control valve short circuit

• P0141 - O2 Sensor heater circuit malfunction (bank 1 sensor 2)

• P0420 - Catalyst system efficiency below threshold (bank 1)

The light came on while I was driving on the motorway (120 kmh).

Are these serious or can I just clear them and drive on?
If any action is required, is this something I can do myself? I love my car but it's costing me an arm and a leg each time I have to take it to the shop and I'm at the point of considering letting it go.

[SD1too]

Hello Erik,

A Midnight blue Connoisseur SE with the 1.8 engine is a lovely car so let's see if we can reduce your anxiety.

Originally Posted by EVS

• P1191 - Oxygen sensor heater open circuit, downstream sensors

RAVE describes the cause of this as a "line break", in other words the wiring to the heater has been damaged. If this has occurred on the sensor's cable then a new one would fix it and that's not expensive.

• P0445 - Evaporative emission control system purge control valve short circuit

RAVE describes this as "short to ground" or "short to battery" which doesn't make much sense. I think what it's saying is that the purge control valve isn't responding. This isn't serious.

• P0141 - O2 Sensor heater circuit malfunction (bank 1 sensor 2)

RAVE says: "heater, electrical, incorrect reading". Well, that's saying the same thing as P1191.

• P0420 - Catalyst system efficiency below threshold (bank 1)

We know from the other codes that an O2 sensor has a heater fault so it won't be providing a correct signal. Therefore the diagnostics thinks that there's a problem with the catalytic converter. In fact it's likely that the converter is working correctly but the downstream sensor isn't able to report this because the heater isn't working.

Are these serious or can I just clear them and drive on?

Yes Erik, you can clear them and drive on, but get that O2 sensor wiring seen to urgently.

Simon

[suzublu]

Just to add to Simon's post, happened to me a few years ago, the sensor wire had melted on the exhaust causing the light. Simply replaced and rerouted it 😎

Sent from my SM-A145R using Tapatalk

[EVS]

Thank you both, glad to hear this time it shouldn't cost too much...
I agree it is a lovely car, but it has become quite the money pit. I don't want to part with it but at the same time I can't keep justifying pouring money into it. Good to know this will be a minimal cost for once.

[SD1too]

Originally Posted by EVS

I agree it is a lovely car, but it has become quite the money pit ...

We all have to remember Erik that our cars are getting old. Yours will soon be 20, mine is 24, and so things will start to go wrong.

I can't keep justifying pouring money into it.

I try to judge the cost of ongoing maintenance against the money I would have to pour into a newer replacement of equivalent quality (which will depreciate in value much faster than the Rover).

Do come back and let us know if the diagnosis was correct. If it is, make sure that the wiring is secured and insulated if necessary from the heat of the exhaust as Suzublu did.

Simon

[EVS]

Originally Posted by SD1too

We all have to remember Erik that our cars are getting old. Yours will soon be 20, mine is 24, and so things will start to go wrong.

I try to judge the cost of ongoing maintenance against the money I would have to pour into a newer replacement of equivalent quality (which will depreciate in value much faster than the Rover).

Simon

Hi Simon, I do realise my car's aging, but even so, spending € 7093.34 since June last year alone is getting a bit steep to my liking. That money could buy me a decent replacement, but at the same time each repair makes me hope that it will be worth it because the car is such a joy to drive - if everything works as it should, anyway.

I've checked the cables under the bonnet and couldn't really find anything wrong. The plug for the cables into the canister purge valve looks rather odd, but it has looked that way for a long time and it's never been an issue.

Is there another sensor other than the one at the start of the exhaust that I should check the wiring of?

Anyway, for now I've also cleared the codes and now have driven over 300 km without the check engine light coming back on, although my car now "jerks" occasionally.

[EVS]

Apologies for the late update.
I was able to check underneath the car and I don't see any molten wiring.
The check engine light hasn't returned but TOAF does show error codes P0445 and P0170.

The car doesn't run smoothly at all, it occasionally stalls when stationary, has trouble pulling away (lack of power and the revs drop when pushing the accelerator from stationary), and when driving, the car shudders and jerks, with a mileage slightly worse than usual.

Are there any further things I could check?

[SD1too]

Hi Erik,

Judging by the engine behaviour you've described and code P0445, try disabling the purge control valve by unplugging its electrical connector (the code may be trying to tell us that it's permanently open).

Simon

[EVS]

There's a problem in that regard: that connector has melted so I can't disconnect it. It has been melted for ages though so I never really paid any attention to it as everything seemed to be working fine. Now of course that means I can't just unplug it. I suppose it's best not to simply cut the wires?

[SD1too]

Originally Posted by EVS

There's a problem in that regard: that connector has melted ...

Ahh, suppose that the heat damage has caused two conductors within the connector to touch one another or be severed. That might explain the fault code.

Cutting the wires followed by a test drive would tell you whether or not the purge valve is the problem. You'd then have to obtain a new connector from a scrapped vehicle and splice it in to the loom. If the purge valve is damaged you'll need a replacement for that.

How on earth did this connector become melted?

Simon