Join Date: Mar 2004
Location: Slave Lake, Alberta, Canada
Feedback Score: 0 reviews
Re: P0381 Glow plug circuit malfunction?????
P0381 is a malfunction with the glow plug indicator lamp circuit. Since this lamp is controlled by the PCM independantly of the glow plug relay, there is no sense in looking to the GPR to cure the code.
That's not to say that there may not be a glow plug concern but that wont result in a "starts then dies" kinda thing, either.
With the key on, battery voltage is supplied to one of the small terminals on the relay. As long as the PCM isn't grounding the relay (to turn it on), battery voltage will be seen at both small terminals. Once the PCM commands the GPR "on", slightly less than B+ will be seen at one small terminal and the other will be close to 0 volts.
For the large terminals.... As long as the relay isn't turned "on", B+ will be seen at one large terminal and 0 volts at the other. When the PCM commands the GPR on, we should see a little less than B+ at both terminals.
This is volt drop testing at it's most basic... it looks and sounds difficult but, in actuality, it is quite simple when we give it some thought. If we can grasp this concept, electrical testing becomes a snap.