P0123 error & MIL light a few days ago and was undriveable

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My Name: The mad hat man

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Posts: 3
Joined: Wed Jan 01, 2020 3:26 pm
Model: C3 2002-2005, Original shape model
Year: 2005 (55)
Engine Size: 1.4 (8v)
Fuel Type: Petrol
Mileage: 80000
Trim Level: Desire
Gearbox: Manual 5 speed
DPF: No
LHD or RHD: RHD (UK)
Engine name: TU3 (75 PS)

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My daughters car came up with a P0123 error & MIL light a few days ago and was undriveable.
I was able to reset both the TPS and ECU and clear the error code. A day or so later the same happened again and the car went in to limp mode. Turning the engine off and back on enabled her to drive to mine (about 2 miles). I reset the TPS and this time checked the TPS_V signal, which, to my untrained eye, looks ok?
TPS trace
TPS trace
However.... Checking a few other parameters, I came across the following....
Catalyst monitor
Catalyst monitor
Does this mean the cat is stuffed, or a sensor?
Could this be the cause of a P0113 error?

Any help appreciated.
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My Name: Arfur Dent

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Model: C3 2002-2005, Original shape model
Year: 2002 (52)
Engine Size: 1.4 (16v)
Fuel Type: Diesel
Mileage: 100000
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Gearbox: Manual 5 speed
DPF: No
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The mad hat man wrote: Sun Nov 08, 2020 12:05 pm My daughters car came up with a P0123 error & MIL light a few days ago and was undriveable.
Hi


P0123 is a TPS fault code
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My Name: The mad hat man

Member
Posts: 3
Joined: Wed Jan 01, 2020 3:26 pm
Model: C3 2002-2005, Original shape model
Year: 2005 (55)
Engine Size: 1.4 (8v)
Fuel Type: Petrol
Mileage: 80000
Trim Level: Desire
Gearbox: Manual 5 speed
DPF: No
LHD or RHD: RHD (UK)
Engine name: TU3 (75 PS)

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Yes. I know that P0123 (and P0121) are TPS errors. That wasnt the Q :)
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My Name: Ozvtr

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Model: C3 2002-2005, Original shape model
Year: 2003 (53)
Engine Size: 1.4 (8v)
Fuel Type: Petrol
Mileage: 80000
Trim Level: Other
Gearbox: Automatic PRND
DPF: No
LHD or RHD: RHD
Engine name: TU3 (75 PS)
Location: Brisbane, Australia.
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With respect to the second picture; a lot of the code readers are set up for the United States emissions tests, which involve a series of tests on the system while the car is driving.
Most of the time just driving the car around will cause those test to be carried out by the engine computer, however resetting the ECU will reset the tests to 'fail' until the tests are completed and passed.

With out access to the instruction manual for the reader I'm not sure what's going on. The picture appears to be for the downstream O2 sensor (bank 1, but there is only 1 bank in this engine anyway). A test value of 655.3 what? Milivolts? If that's correct that shows that the output from the catalytic converter contains too much oxygen and is considered a 'fail'. Is this data instantaneous or average or peak or what?
But this is a 'fail' of the catalytic converter and will not effect the engines performance (unless it's something else causing a lean mixture). Is the check engine light still on? If no, then the car doesn't consider this value a failure of the catalytic converter. It's a long story. I don't think it's relevant.

The TPS data appears to be in % (I would have to read the instruction manual to see) and appears to show someone pushing the throttle all the way down and then releasing it.
It appears that the 'idle' point is 16.6% but just before and just after pushing on the peddle it drops to 9%. The maximum output is 82.4%. Unfortunately there is no time base so I don't know how long it took to perform this procedure. Seconds, miliseconds? I do not know if you are monitoring the throttle body or peddle position. This appears to be normal either way...if you confirm my analysis.
You would need to monitor the live data for the throttle peddle output and throttle body butterfly position to see where your TPS error is (when it occurs).

There is a small adapter cable in the dash wiring loom connected to the throttle peddle that is known to cause problems.

P0113 error would be the temp sensor in the MAP sensor located on the front left hand side of the inlet manifold plenum. The MAP sensors are pretty reliable. Check for corrosion on connector pins of the sensor or the engine ECU connector.
My Name: The mad hat man

Member
Posts: 3
Joined: Wed Jan 01, 2020 3:26 pm
Model: C3 2002-2005, Original shape model
Year: 2005 (55)
Engine Size: 1.4 (8v)
Fuel Type: Petrol
Mileage: 80000
Trim Level: Desire
Gearbox: Manual 5 speed
DPF: No
LHD or RHD: RHD (UK)
Engine name: TU3 (75 PS)

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Thanks Ozvtr.
The first picture is me pressing the throttle pedal to the floor and releasing it.. Timescale = "slow and steady" ;). Bearing in mind my calibrated right foot, I thought it showed a reasonably accurate response, which leaves me with "what is causing the P0121 error code (not P0123 as previously stated).
As for the bank1 "fail", I assume (dangerous, i know) that with only 1 bank, the reading defaults to Bank1.

My problem is that the car goes into dangerous undriveable limp mode when the P0121 mode and MIL are light. I am trying to fault find, but its a bit like the blind leading the blind and it is only me trying to fix the fault, to help my daughter. I do not wish to go down the route, if possible of replacing one thing after the other as money is non existent!

Would you agree that the P0121 error is not likely to be throttle pedal/position sensor? This fault can be cleared (temporarily) by a TPS reset.
If not, do you think the Cat problem, if it exists, could cause these random problems of the car being undriveable? As for what the values are, the car was on idle when I checked the values. I am not sure what the values are, except that it appears that it is a lot higher than it should be.

What to do next???
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My Name: Ozvtr

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Posts: 942
Joined: Wed Jul 10, 2019 3:31 am
Model: C3 2002-2005, Original shape model
Year: 2003 (53)
Engine Size: 1.4 (8v)
Fuel Type: Petrol
Mileage: 80000
Trim Level: Other
Gearbox: Automatic PRND
DPF: No
LHD or RHD: RHD
Engine name: TU3 (75 PS)
Location: Brisbane, Australia.
Has thanked: 36 times
Been thanked: 252 times

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Yes, typically there is one cat and one downstream (cat monitor) O2 sensor for each exhaust pipe. 'V' engines (V6, V8) typically have 2 exhaust pipes (bank1 and bank2). If the engine only has one exhaust pipe that defaults to bank1.

I would forget about the cat problem. It's only part of the anti pollution system and will not effect the performance of the engine.
The downstream (cat monitor) O2 sensor voltage out put should stay around 400(miliVolt) (0.4V) and not fluctuate much. The more it fluctuates, the worse the converter is performing. If it gets to a peak of 1V and of a low of 0V, the converter is not working at all! It still wont effect the engines performance however. The car may fail MOT, but I'm not familiar with that. If the engine light only comes on when the TPS fault occurs then the car is not concerned about catalytic converter, despite what the scanner says.

There is an inter connector/adapter behind the glove box that can cause trouble with the throttle. questions-about-a-petrol-powered-citroe ... t2432.html

The problem is that it could be the accelerator peddle, the throttle body or the wiring. Use your scanner to monitor the peddle or throttle position. One of them will drop to 0 or up to +ve when the fault occurs. If the one you are monitoring works OK during the fault then the problem is the other.
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