MGTF 135 from 2003: error codes P0118, P0130, P0563, P1185

[ppo]

Hi,

I'm having some problems with my TF135 from 2003. The car is driving very smooth and has no miss-firing or showing other symptoms (fans running constantly), but following 5 error codes are saved in my MEMS:
- P0118 Coolant temperature sensor, signal too high
- P0130 O2 Sensor Circuit Malfunction (Bank 1 Sensor 1)
- P0563 System Voltage High
- P1185 Upstream (pre-catalyst) Oxygen Sensor Heater Electrical Fault
- P1539 Power to A/C Clutch Circuit Over current --> can be ignored

When deleting the errors, they come back instantly when staring the engine.

Following parts have already been changed:
- battery
- alternator
- pre-cat Oxygen sensor
- post-cat Oxygen sensor
- coolant temperature sensor

Checking all connectors and earth points didn't help.
I'm also having an additional wide-band lambda sensor installed just after the flex section and the reading is showing stoichiometric values when driving. This means, that the pre-cat oxygen sensor is working correctly.
Testing the wiring of the coolant temp sensor wiring showed no issue or broken wire. Could it be that the new coolant temp sensor is faulty?
Is there a common wiring between the coolant temp sensor and the pre-cat oxygen sensor?

Any suggestion welcome. Thanks.

[talkingcars]

Fans running constantly is a sign of a failed ECU coolant temp sensor.

I think I'd start by checking the plugs in to the ECU.

[ppo]

Sorry, but I used “fans running constantly” only as an example.
I should have been writing instead:
“The car is driving very smooth and has no miss-firing nor showing any other symptoms nor are the fans running constantly, but following 5 error codes are saved in my MEMS:”

[Rob Bell]

Which diagnostic system are you using ppo?

Interesting that these faults return whenever you clear them and then restart the engine. Also curious that the engine is running faultlessly: you'd kind of think that it would be like a bag of nails with so many error codes!

2003 is a transition year for the electrical architecture: do you have a Lucas or Pektron immobilizer?

One quick thought: what is the voltage when the engine is running: is the alternator over-charging? The Bosch alternators aren't renowned for being the most reliable.

[ppo]

Hi Rob. Thanks for your reply.
I have the Lucas one and I’m using the last version of Pscan on my laptop, so I don’t think that the OBD reader is the cause. The voltage measured at the battery is 13,8V when the engine is running.
When disconnecting the coolant temp sensor, the readings go down to -40°C. Connecting the 2 connector pins together makes the reading go up to 284°C. So the wiring for the temp sensor to the ECU connector seems ok. Leaves me with a faulty sensor or ECU connector.
For me it‘s a problem with the engine loom, but finding an used one for my VIN with air conditon isn‘t easy, and at the moment I‘m not ready to pay over £300 for a new one.
In a next step I’ll connect the lambda with a separate loom to the ECU connector and see what happens.
Fingers crossed.

[Rob Bell]

I'm a bit suspicious of the engine loom too given the number of faults being recorded. Depending on year, different sensors were clustered together on different sublooms. If all these sensors are on the same subloom, then I would think that the problem comes down to either the loom (and specifically the earth for that loom) or the connector block.

[ppo]

Just a thought:
Could an incorrect tension of the alternator belt be the reason for the voltage and all the resulting problems ???

[Rob Bell]

Not unless it was slipping - and then generally, the charging voltage would likely be maintained less the belt was failing to turn the alternator at all.

[ppo]

Thanks Rob.

[ppo]

A bit of a frustrating update.

- I first replaced the MEMS with a newlyprogrammed one from Mark Stacey without any other modifications and all the errors were still present.
- Checking again the O2 and coolant temperature sensor loom didn't show any problems with the cables or connectors.
- Finally I checked the 2 MEMS connectors and more precisely the pins of the coolant temp. sensor.I bend them a bit with a screwdriver.

After reconnecting I cleaned the errors and stated the engine. After reding again the errors, P0118 (Coolant temperature sensor, signal too high) had disappeared.
To be sure, I bend back the pins again and immediately the error reappeared. So the root cause was found for the P0118 error.

I also bend the pins for the O2 sensor and connected the MEMS again. After deleting the errors I started the engine and leave it running for several minutes. I even moved the MEMS and the connector looms around, but when checking, NO eror codes were stored. Problems finally solved.

I put everything together and went for a good run on the country roads.
One hour later, I put the car back in the garage and connected the Pscan OBD2 reader for a final check, and the following errors reappeared:

- P0130 O2 Sensor Circuit Malfunction (Bank 1 Sensor 1)
- P0563 System Voltage High
- P1185 Upstream (pre-catalyst) Oxygen Sensor Heater Electrical Fault
- P1539 Power to A/C Clutch Circuit Over current --> can be ignored

I seems, that due to the movements during driving, the pins of the MEMS connector loose contact randomly.
I now have 3 options:
1- bend the corresponding connectors a bit more
2- solder in an used connector
3- install a complete new engine loom (YSB000970)

[talkingcars]

Does your ECU plug have the clamp still fitted?

[talkingcars]

Does your ECU plug have the clamp still fitted?

If you areunsure post some photos.

[ppo]

Yes the clamp is still on.

[ppo]

Good news! Seems that I managed to find the troublemaker after all. Driving the car for now 3 days and checking after every run if any error was saved in the MEMS. Until now, no error appeared. Fingers crossed.

The problem were the connectors in the ECU plug for pins:
1 Upstream oxygen sensor heater – output
28 Upstream oxygen sensor ground - input
41 Upstream oxygen sensor negative - input
And also the connector for the lambda pre-cat lambda sensor had some problems for the heater signal.
Bending the corresponding pins to have a firmer grip helped to resolve the problems.

[colintf]

That's great news Pascal

[Geoff.F]

Have you invested in an Aerosol of Contact Cleaner ???
Geoff.F

[ppo]

Cleaning the contacts was the first operation I did, but with no effect.
Due to vibrations and working on the car during the last 15 years, the female pins inside the connectors were bend and too wide resulting in poor contact between the parts.
I prefer when pure mechanical parts break than trying to resolve P0xxx error codes.
This is the problem with the actual cars, and it will be much more visible in the future, when you'll need an informatics guru instead of a mechanic to repair your car. They will change parts of your car, if broken or not, only because the computer has stored an specific error code, without trying to look for the initial reason of the error. And unfortunately your bill will increase proportionally.

[BodgeItAndScarper]

I prefer when pure mechanical parts break than trying to resolve P0xxx error codes.
This is the problem with the actual cars, and it will be much more visible in the future, when you'll need an informatics guru instead of a mechanic to repair your car. They will change parts of your car, if broken or not, only because the computer has stored an specific error code, without trying to look for the initial reason of the error. And unfortunately your bill will increase proportionally.

I expect a century ago some chaps were grumbling about how hard it had become to fix cars 'now they have all that bodywork in the way', and that 'you used to be able to see what was broken, now you just hear a noise' the

Fault codes are just symptoms, they're not the problem. They're an additional tool which can help track down the problem. And bad mechanics can play parts roulette on any machine, however simple.

[ppo]