Hey There Fellow Diesel Lovers. I have a 1996 chevrolet k2500 Suburban with 110,000 miles. my service engine soon lamp has turned on and I ran the code, p0380 So I changed the glow plugs. The light still stays on even after i cleared the code with the scanner. I am guessing maybe it is the glow plug relay? I needed new plugs anyway, everything on the truck is original except the batteries and starter. Any Ideas ? your help would be greatly appreciated.
On the 1994 and newer pickups, the glow plug relay is simply that- a relay. It looks just like the previous unit that was a combination controller/relay. For 1994 and newer, the computer takes over the control function.
Check for battery power on one of the large studs on the relay.
Then have someone turn on the ignition key. The relay should snap in, and there should be battery voltage present on the second terminal, connected to the glow plugs.
Is the WAIT light in the dash working? That is connected to the actual glow plug harness, and if it's lighting, it indicates power is passing through the relay, to the glow plugs.
I believe there's a fusible link for each bank, so check for power at both banks.
And, as always, check all battery, engine, body, and frame grounds.
I have a 99 diesel van and a 99 suburban. The van was having trouble starting in the winter and, like yourself, thought the glow plugs might need to be changed. I had no problems and 80k miles so why not. The problem was the glow plug relay after all. Once replaced, the van started without the block heater being plugged in.
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