tech advice

[agt]

I have a 2005 duramax 6.6L. What would cause the glow plug indicater lite to stay on continuously with the key in the on position and other times it comes on for a split second and goes out. The lite is not consistant anymore. I checked the glow plugs with an ohm meter and they are all ok.

[More Power]

I have a 2005 duramax 6.6L. What would cause the glow plug indicater lite to stay on continuously with the key in the on position and other times it comes on for a split second and goes out. The lite is not consistant anymore. I checked the glow plugs with an ohm meter and they are all ok.

How long is "continuously" with the key in the ON position?

Otherwise, the computer decides whether to give the glow system a full cycle or a short one, depending on engine temp.

Jim

[agt]

Jim,

Thanks for responding.

When the glow plug lite worked properly it stayed on for 2-3 secs. @ the most before going out, no matter if it was cold or hot outside. Now it will not go out, @ times, no matter hot or cold out. I don't let it on for too long cause i'm afraid of damaging glow plugs. Other times during hot or cold starts the lite will come on for a split second then back out. And sometimes it will come on and go out in 2-3 secs. like its supposed to.

By the way,the engine never has hesitated to start.
Could it be the glow plug controller?

Andy

[DmaxMaverick]

Glow plug timing is determined by the PCM, which merely triggers the relay (and the GP/WTS lamp). The glow cycle is dependent on many inputs, including ambient temp, ECT, and feedback voltage. A failing/failed relay can cause extended glow times, as can several failed plugs or the heater. If you aren't seeing the SES lamp, and a corresponding pre-start system code (P0380, etc.), the likely suspect is a sensor input, namely the ECT (different from your gage sender), or a sticky relay. There was a recall regarding glow plug operation and/or poor glow plugs at one time (2004-2006 models, IIRC). Check with your dealer to determine if yours is/was a candidate. The correction was a program calibration (update) and/or GP replacement.

Starting quality can't really be judged by the conditions of the glow system, except in very extreme cold conditions (sub-zero). These engines will fire off, almost normally, down to very low temps. At this time in the U.S. with the coldest temps I'm aware of, the only ones missing the glow plugs are the EPA.