...as I had cause to go out yet again, this time I cleared the fault before recording data.
At idle, just after starting.
C3 P0402 EGR Excessive Flow
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MikeT
- Posts: 4808
- Joined: 11 Jun 2007, 16:17
- x 232
Re: C3 P0402 EGR Excessive Flow
Here's some more
...as I had cause to go out yet again, this time I cleared the fault before recording data.
At idle, just after starting. Eventually the EGR OCR flatlined again at 5% so I pulled over and checked for the fault data.
...as I had cause to go out yet again, this time I cleared the fault before recording data.
At idle, just after starting. Eventually the EGR OCR flatlined again at 5% so I pulled over and checked for the fault data.
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EDC5
- (Donor 2020)
- Posts: 1218
- Joined: 01 Jul 2017, 21:48
- x 130
Re: C3 P0402 EGR Excessive Flow
I'm struggling with this one. My car has always registered a higher measured air flow compared to the reference value and I've had a permanent fault based on that stored in the ECU but it never brings on the warning light and disappears, sometimes for weeks at a time.
Does the car drive ok? no hesitation or black smoke suggesting the EGR is stuck open?
From the pic on the last page it seems that the EGR is vacuum operated and the only way for the car to detect EGR operation is the reduction of air flow as shown by the MAF. Perhaps id the MAF generates some erroneous air flow values the ECU stops EGR regulation until the air flow comes back within spec.
Could you drive without the MAF connected and see what effect that has on the engine?
Does the car drive ok? no hesitation or black smoke suggesting the EGR is stuck open?
From the pic on the last page it seems that the EGR is vacuum operated and the only way for the car to detect EGR operation is the reduction of air flow as shown by the MAF. Perhaps id the MAF generates some erroneous air flow values the ECU stops EGR regulation until the air flow comes back within spec.
Could you drive without the MAF connected and see what effect that has on the engine?
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MikeT
- Posts: 4808
- Joined: 11 Jun 2007, 16:17
- x 232
Re: C3 P0402 EGR Excessive Flow
I think Stewart and wheeler called it right from the off
The data shows more air is passing the MAF than calculated.
What's more, the ECU is commanding 85% EGR OCR (until it gives up and flags the fault), which I believe is the absolute maximum it can ask for.
Then, with the EGR taken out of the calculations, the Reference and Measured values perfectly match!
Yes, it generally drives ok, pulls well for the little engine I guess, though I've little to compare it to.
I intend to give the MAF a good clean as it's so easily accesible so yes, can disconnect the plug too but not sure if this existing fault would only confuse the matter at this point?
The data shows more air is passing the MAF than calculated.
What's more, the ECU is commanding 85% EGR OCR (until it gives up and flags the fault), which I believe is the absolute maximum it can ask for.
Then, with the EGR taken out of the calculations, the Reference and Measured values perfectly match!
Yes, it generally drives ok, pulls well for the little engine I guess, though I've little to compare it to.
I intend to give the MAF a good clean as it's so easily accesible so yes, can disconnect the plug too but not sure if this existing fault would only confuse the matter at this point?