|
|
Post by chippie on Oct 19, 2020 17:01:11 GMT 1
ECP lamp illumiinated on dash along with Stop/Start system error. Seems to go into Limp mode.
Twice this occurred in the last two days...First thing in the morning.
Fault light cleared after turning off the engine and then reatarting.
Took the car to the dealers as it was under warranty ( thank goodness! )
They scanned the vehicle and found it had a fuel sensor fault logged.
Quizzing the service guy, the sensor is on the injection rail, so its the high pressure sensor. Same replaced, faults cleared and car road tested.
So is the fuel rail sensor an analog one rather than a simple switch? Why would the fault clear and then come back? Out of limits I guess?
|
|
|
|
Post by valhalla on Oct 19, 2020 22:59:55 GMT 1
Has this actually fixed the problem? That is, does it no longer flag a fault after car has been stood and is cold?
I'm quite sceptical that the high pressure fuel rail sensor is the culprit here, unless it has a mechanical fault when cold. More likely that the fuel rail pressure control is poor on a cold-start, and that can be down to many things, not least the simplest problem of them all, low-pressure fuel drain-back/air ingress.
Most rail pressure sensors are analogue scalar-type units with a voltage output back to the ECM to indicate rail pressure. Because of the huge range of pressures that they have to read, they can be quite sensitive to mechanical loads (poor fitting or misfitted sealing washers causing the sensor nose to distort) as well as electrical noise, and I believe there was a move towards "smart" sensors with PWM output to deal with the latter problem (in the same way as MAF units with PWM output). Signal noise is a bad thing, as the sensor is the main feedback to the ECM for a number of safety-critical controls, and the ECM needs to respond fast to pressures that are shooting upwards.....
It would be great to be a fly on the wall at your VW dealership; I reckon that you now have a new bit of software in your ECM, whatever else was done.........  |
|
|
|
Post by Noberator on Oct 20, 2020 11:12:30 GMT 1
These modern vehicles are getting more complex for the average person. Not that your average Chip  I mean that in a nice way by the way.  Here is a list of different possible causes of limp-mode. Engine boost control, overboost/underboost Faulty engine sensors Faulty engine components Engine wiring issues Transmission issues Transmission wiring issues Brake system wiring issues Limp mode is basically to prevent damage so limits the engine to about 3000 rpm ish to make sure that you won’t blow or damage any engine parts. Because many car owners do not take enough notice of the engine light or dash warning lights IMO and the engine control unit sets itself to limp mode and shuts off the turbo boost completely to limit the engine rpm. |
|
|
|
Post by chippie on Oct 20, 2020 11:26:22 GMT 1
Errrm thnx for the kind average words......  Checked the car this morning.....Switched the ignition on.....all good...No warning lights at all... Took car for a spin, still nothing. Went to Morrisons for diesel, all good..... So, It looks like the fault at the moment is non-repetative..... Going away Friday for a few days with the caravan, so we'll see how it performs then. It does seems to be a little livelier than before? Mebbe its me  I've not looked under the bonnet yet to see if there are any signs of replacement fitted parts, so Valhalla's thoughts remain so.... |
|
|
|
Post by Noberator on Oct 20, 2020 11:47:25 GMT 1
Errrm thnx for the kind average words...... Checked the car this morning.....Switched the ignition on.....all good...No warning lights at all... Took car for a spin, still nothing. Went to Morrisons for diesel, all good..... So, It looks like the fault at the moment is non-repetative..... It does seems to be a little livelier than before? Mebbe its me I've not looked under the bonnet yet to see if there are any signs of replacement fitted parts, so Valhalla's thoughts remain so....   Hopefully car behaves itself. |
|
