Can't erase DTC

madcatman · Post by **madcatman** » 10 Mar 2011, 04:59

I have a 2004 UK spec. V50. Now and again I'm getting an 'engine service' warning. The code is always P0380, which is a glow plug problem. The codes were cleared when the car was last at the dealer, and the warning has come up a couple of times in the six months since.

I got a Launch Creader V codereader box which works exactly as the manual describes and reads the codes ok, but when I tell it to erase the codes I get a message back that the codes were not erased, and they are still there when I recheck.

Has anyone else seen this - is there something about the V50 that prevents non-dealer units resetting codes?

Thanks, Steve

Post by **billofdurham** » 10 Mar 2011, 11:36

Welcome to Matthew's Volvo Site.

Most scan tools will erase codes - after you have fixed the problem. However, the code will usually go away after a certain number of driving cycles, if it isn't repeated.

P0380 is a faulty signal to the glow plug relay. Check the glow plug relay connector for oxidation and contact resistance. Other checks are on the wiring to see if there are any breaks or short/open circuits. Final checks involve the use of a breakout box as they are done on the ECU.

Bill.

madcatman · Post by **madcatman** » 11 Mar 2011, 00:48

Surely the code reader can't know or care if I've fixed the fault. I instructed it to erase the codes and it didn't. I'm trying to figure out if it's a dud unit or there's something odd about the V50 and that's difficult without another of either to compare with.

madcatman · Post by **madcatman** » 11 Mar 2011, 04:21

It seems I'm on a steep learning curve here. Am I right in thinking I can't reset these codes because the car control unit sees the fault is still there at switch on, even though the glow plugs probably aren't activated?

I was expecting behaviour like chasing an O2 sensor warning on our other car (actually a tiny vacuum leak) where I could reset the code after each warning light came up.

Steve

Post by **billofdurham** » 11 Mar 2011, 11:35

Steve, you have beaten me with the answer. This is from one of my service books:

if the problem which generated the trouble codes is not repaired, the codes will reappear shortly, when the PCM again detects the problem.

On a diesel engine the glow plugs relay engages every time the ignition is switched on, even if the glow plugs are not energized.

As far as I'm aware there is nothing different on the V50 to stop you erasing the codes.

Bill.