mk1BDA
New Member
Hi everyone, this is my fist post on this forum. Sorry for not posting an introduction as yet but I have a major problem with my A2 and i'm hoping someone may be able to help.
A couple of weeks back I started the car and after idling for a few seconds its started to run really rough (like it wasn't firing on all cylinders). It revved freely and sounded OK above 1200 rpm, but at idle the poor running returned and it would stall. I restarted and the same thing happened, ran rough and died, then I haven't been able to get it to start since.
The engine will crank, but it will not catch / fire up. The starter just turns the car over. It will not start with easy start either.
I've replaced:
Coil Pack
Spark plugs
HT Leads
Coolant temp sensor
Checks:
Check and clean of all earth points
Battery is fully charged
Fuel pump primes system with ignition
New fuel has been added and fuel appears to be getting through
Good compression
Inspect TB and clean. TB actuator internals appear contamination free and in good condition.
EGR valve looks dirty and old.
Diagnostic tool reading is intermittent. Switching the ignition on, I notice that the EML light is very quick to turn off. In this scenario, where the EML lights and almost instantly disappears (before ABS light for example). I am unable to make a talk to the vehicle ECU.
Occasionally, the EML will appear and stay lit if I leave the ignition on for a period of time only then can I talk to the ECU and I have been able to pull codes relating to the Throttle Actuator and EGR Valve. These codes are
p0638 Throttle Actuator Control Range/Performance B1
p0403 Exhaust Gas Recirculation Circuit Malfunction
The throttle butterfly is unresponsive, does not move or appear to get power or commands with ignition or throttle input. I believe the throttle butterfly should cycle / self check with ignition but could be wrong?
The EGR appears to click with ignition. I have noticed that, the EML light appears and disappears as soon as the EGR clicks (1-2 secs after turning key to ign on). In this scenario, as I mention above i have no ECM comms, although I can run a scan, it just reports modules such as ABS and Instrument panel cant talk to the ECM (P01314 for example).
Is there an electrical relationship between the TB and EGR that would prevent communication with the ECU?
If I unplug the EGR, the EML disappears altogether does not light up at all during ignition cycle. Disconnecting the TB makes no difference.
I find it really unusual that disconnecting the EGR results in no EML illumination at all. Having it connected, always gives the EML light (albeit for 1-2 secs) but there appears to be a problem either here or with the throttle that is somehow shorting out the ECU resulting in a no comms situation.
If anyone has any ideas what I am looking at here, or could provide a circuit diagram for these elements that would be much appreciated.
A couple of weeks back I started the car and after idling for a few seconds its started to run really rough (like it wasn't firing on all cylinders). It revved freely and sounded OK above 1200 rpm, but at idle the poor running returned and it would stall. I restarted and the same thing happened, ran rough and died, then I haven't been able to get it to start since.
The engine will crank, but it will not catch / fire up. The starter just turns the car over. It will not start with easy start either.
I've replaced:
Coil Pack
Spark plugs
HT Leads
Coolant temp sensor
Checks:
Check and clean of all earth points
Battery is fully charged
Fuel pump primes system with ignition
New fuel has been added and fuel appears to be getting through
Good compression
Inspect TB and clean. TB actuator internals appear contamination free and in good condition.
EGR valve looks dirty and old.
Diagnostic tool reading is intermittent. Switching the ignition on, I notice that the EML light is very quick to turn off. In this scenario, where the EML lights and almost instantly disappears (before ABS light for example). I am unable to make a talk to the vehicle ECU.
Occasionally, the EML will appear and stay lit if I leave the ignition on for a period of time only then can I talk to the ECU and I have been able to pull codes relating to the Throttle Actuator and EGR Valve. These codes are
p0638 Throttle Actuator Control Range/Performance B1
p0403 Exhaust Gas Recirculation Circuit Malfunction
The throttle butterfly is unresponsive, does not move or appear to get power or commands with ignition or throttle input. I believe the throttle butterfly should cycle / self check with ignition but could be wrong?
The EGR appears to click with ignition. I have noticed that, the EML light appears and disappears as soon as the EGR clicks (1-2 secs after turning key to ign on). In this scenario, as I mention above i have no ECM comms, although I can run a scan, it just reports modules such as ABS and Instrument panel cant talk to the ECM (P01314 for example).
Is there an electrical relationship between the TB and EGR that would prevent communication with the ECU?
If I unplug the EGR, the EML disappears altogether does not light up at all during ignition cycle. Disconnecting the TB makes no difference.
I find it really unusual that disconnecting the EGR results in no EML illumination at all. Having it connected, always gives the EML light (albeit for 1-2 secs) but there appears to be a problem either here or with the throttle that is somehow shorting out the ECU resulting in a no comms situation.
If anyone has any ideas what I am looking at here, or could provide a circuit diagram for these elements that would be much appreciated.