Maybe I have asked or maybe there is more info on this site about the P 0380 code . I need more info . Last week my service engine light came . I whipped out my trusty scan tool and showed the P 0380 code . My question is could one glow plug be out and this code comes up ? I thought with this code it meant either the relays that turn on the controller were bad or the controller itself was bad . I have seen all the you tubes for checking the relays and the controller . But I was wondering if one glow plug or any glow plugs were bad that a code. would be set ? I am old school and when my 6.2 was hard to start then I checked my glow plugs because 90 percent of the time that was the issue
Need info on a P0380 code
- Thread starter Duroman
- Start date
Make: Chevrolet
Code: P0380
Definition: Glow Plug Range/Performance
Description: Engine cranking, Glow Plugs "on", and the PCM detected glow plug voltage was below 4.0v, or with the plugs "off", it detected the glow plug voltage was over 4.0v, or with the Glow Plugs commanded "on", over a 2.0v difference between system voltage and glo
Cause:
Related Service Bulletins:
View This Bulletin
Code: P0380
Definition: Glow Plug Range/Performance
Description: Engine cranking, Glow Plugs "on", and the PCM detected glow plug voltage was below 4.0v, or with the plugs "off", it detected the glow plug voltage was over 4.0v, or with the Glow Plugs commanded "on", over a 2.0v difference between system voltage and glo
Cause:
- Glow plug relay control circuit is open, shorted to power, or the ground circuit is open
- Glow plug relay is stuck in "on" position causing constant power
- Glow plug relay is damaged or has failed
- PCM has failed
Related Service Bulletins:
View This Bulletin
Federal or Cali emissions LB7? If federal, it's your glow plug relay.
On a federal emissions truck, P0380 is a glow plug relay failure, stuck closed or not making connection. All 8 glow plugs are connected in parallel to the glow plug relay and no codes will show up with any open glow plugs. P0380 is set when the glow plug relay is commanded on and the glow plug voltage signal is less than 4v, or the glow plug relay is commanded off and the glow plug signal voltage is over 4v.
Cali emissions LB7 is different. All 8 glow plugs are individually connected to the glow plug controller. The monitor signal feedback from the glow plug controller to the ECM ranges between 5-6.2v with no failed glow plugs. With 1 open glow plug the feedback voltage is 2-3v, 2 open glow plugs the feedback is 1-2v, with 3 opens it drops even lower, etc. On the cali LB7s, P0380 is set when the plugs are commanded on and the feedback signal to the ECM is not between 5-6.2v or the plugs are commanded off and the feedback is more than 2v.
On a federal emissions truck, P0380 is a glow plug relay failure, stuck closed or not making connection. All 8 glow plugs are connected in parallel to the glow plug relay and no codes will show up with any open glow plugs. P0380 is set when the glow plug relay is commanded on and the glow plug voltage signal is less than 4v, or the glow plug relay is commanded off and the glow plug signal voltage is over 4v.
Cali emissions LB7 is different. All 8 glow plugs are individually connected to the glow plug controller. The monitor signal feedback from the glow plug controller to the ECM ranges between 5-6.2v with no failed glow plugs. With 1 open glow plug the feedback voltage is 2-3v, 2 open glow plugs the feedback is 1-2v, with 3 opens it drops even lower, etc. On the cali LB7s, P0380 is set when the plugs are commanded on and the feedback signal to the ECM is not between 5-6.2v or the plugs are commanded off and the feedback is more than 2v.
Mine is Federal your info will help ....I just didn't want to have to replace glow plugs if I don't have too
There are actually 2 relays inside the black plastic block looking thing on rear of the drivers side valve cover, but I replaced my whole module. One interal relay is for the intake heater, the other for the glow plugs. If one is not working correctly the other may be not too far behind.
Actually I am not sure the relays inside the module are individually available. Google "LB7 glow plug relay" and there's many pictures available on the web of the black box.
Actually I am not sure the relays inside the module are individually available. Google "LB7 glow plug relay" and there's many pictures available on the web of the black box.
Okay I just tried to use my scan tool and it shows 0 volts to the intake heater and glow plugs . I need some help . I have tried to remove the fuse housing to get to the fuse that powers all this stuff . I can remove the top but not the sides that hide the glow plug fuse . Is there away or a trick .Tried you tube and they just show it coming out with just there hands
Right at the fender is a clip (circled in red) and on the passenger side of the box are 2 detents (circled in red). Just pull those 2 lowest spots away from the box and The clip at the fender. You might have a plug that’s also mounted to the side towards the firewall side of the box.
