Diagbox Refusing To Clear Faults?

[sifaan]

Hi

 

For the past 2 weeks or so the car (c5 Mk1, 2.0 petrol, AL4 auto) has been having an anti-pollution fault, so I got an electrician with a lexia (or more precisely Diagbox) to look at it and he cleared the faults on the system and it got rid of the message (and the check engine light on the dashboard)

 

When he was done with the job, everything seemed fine. A little later I noticed that the car was on low, so I started it up, raised it to normal and switched off again.

 

Later, I needed to move the car (it was blocking another car in the parking lot) and I switched on and got gearbox fault message (as well as gear lights blinking in the display) - but I was able to put the car into reverse, and move it to a different place (but forward was only 3rd gear I suspect).

 

Since then, the gearbox fault appears whenever I switch on the ignition, and I have not been able to put the car in reverse either (the brake pedal depresses fully, but I can't move the gear selection lever out of P). Resetting BSI by battery removal has not helped.

I don't remember seeing the fault when I lowered the car although it was possibly there then as well.

 

I haven't been able to get the electrician back to take a look at it; but I resurrected my old chinese lexia and got it working on diagbox 5.02 (and today on 5.20). The unit shows 3 faults on the BSI:

"Permanent fault Communications fault with the engine management ECU"

"Permanent fault Communication fault with the automatic gearbox ECU"

"* Permanent fault Boot lighting command"

 

The text of the first is in blue, the others are black; only the third has an asterisk in front (although I don't know what it means).

Can't get more info on any of the errors.

 

When I try to clear the faults, I get the message

"This command will erase the fault log

However, this one has not yet been consulted

erasing is impossible"

 

What could I try?

 

Thanks

/Sifaan

 

 

 

[qman3428]

Check the battery is fully charged otherwise you will get random faults, allso there was an issue with a small crack in the engine fuse box which caused gearbox issues, again worth looking for as it ties in with only getting 3rd.

[sifaan]

Interesting that you mention the battery - the incident (fault clearing and subsequent gearbox fault) happened on Monday - tried battery reset several times to no avail.

On Tuesday I was trying from about 6pm to midnight to get the fault cleared (it took Tuesday day to get it configured on my Mac) and there were no issues with the battery even then

Yesterday I was away, and today when I tried again I did get an economy mode active warning which I didn't take much notice of - but just now when I tried to start the car, it didn't have enough juice even to light up the dashboard (it did initially, but at the first attempt to start it died)

Had to jump start the car, and now leaving it on idle a bit to charge up the battery.

 

Can't imagine what could cause the battery to drain cos no lights were on (but now took the precaution of removing the boot lights since there was some fault associated with them) and will see what Diagbox says shortly (currently trying to update 5.20 to 5.29, the latest I can apparently get without flashing the unit)

[sifaan]

So, the battery proved to be the culprit after all

Yesterday I tried twice with the engine running for about 20 mins, but that wasn't enough to get it out of it's sulk and didn't have time to try further yesterday

Later that night I managed to get diagbox upgraded to 5.29 (it takes a very long time to "install the internet update")

 

Today I tried running a full diagnostic with the engine running - and while the diagnostic was running the car again went in to economy mode (the glovebox light was on since the glovebox was open, but can't imagine that putting the car into economy); I switched off and started again, and lo-and-behold, the gearbox fault was gone

(the boot lighting error still remains, together with some other random error in the BSI, and I still can't clear them, but at least the car is moving again)

 

Many thanks!

[sifaan]

So, the car ran fine for a few weeks, and then the problem surfaced again - initially intermittently, but now for past 2 weeks it's always there. the battery is fully charged (even took it out and got it independently tested) so it seems unlikely that the problem is with the battery.

 

any suggestions what else I could try?

[sifaan]

Finally got the faults cleared with diagbox; there were some faults in the transmission ECU relating to pressure regulation, so got the solenoids replaced (apparently thats the fault that comes when the solenoids start misbehaving) and since then (touch wood) it's been behaving