I have looked @ hte no start list in the forum, but i will ask my question. I have a 1997 Chevy 3500 6.5L Turbo. I am currently not getting the glow plug curcuit to work. Here is what i know so far. There is power to the relay. ON the 3 wire plug, i ahve 12V @ the red wire when the key is turned, i have ground @ the black wire, but i am not getting 12V from the ECU to turn the circuit on. The yellow wire is fine from the relay to the ECU. Therw is 12V to the ECU, and ground. I can't not connect to the ECU through the scan tool. Some Backround. The truck ran great will last week. i was replacing the solonoid for the plow and cleaning up a ground on the passengers side fender. Once back together, the fuel and temp guage went crazy. turned the truck off, and checked the ground. The guages now work fine, and if the ground is removed they still work. think the ground is for the front headlight area. Also my heater doesn't work. Sometimes it works on high, but not all the time. I have a feeling the ECU is bad, but am not sure how to properly test it, as i don't want to throw parts @ it. Thank you for any help.

did you get 12v at the 2 big studs when you turn key on if not bad glow plug relay

no, i only get 12V @ one stud. But i am not geting the 12V from the computer on the yellow wire to tell the relay to turn on.

did you check 2 ECM and Glow plug fuses under hood

All fuses are good. The ECU is getting power, but i don;t think it's turning on.

do here glow relay click

the relay is not turning on, and the wait to start light is not comming on eather

sorry this didn't catch my eye check the fuse for the The OBD II connector is powered by the aux cig ligther circuit.

see the pics for diagnosing

Circuit Description

The glow plug system is used to assist in providing the heat required to begin combustion during engine starting at cold ambient temperatures. The glow plugs are heated before and during cranking, as well as during the engine operation. The PCM controls the glow plug ON times by monitoring coolant temperatures and glow plug voltage. This system check will check the glow plugs and the glow plug feed circuit coming from the relay.

Diagnostic Aids

If the glow plug relay is stuck in the ON position, check for proper operation of glow plugs. When glow plugs are commanded ON by the scan tool, an internal PCM timer protects the glow plugs from

damage by cycling them ON for 3 seconds and then OFF for 12 seconds. Most glow plug system failures are covered by DTC P0380. If no DTCs are stored, vehicle is hard to start and white smoke is present during cranking or after the vehicle is started. The most likely cause of failure is the glow plugs.

Test Description

Number(s) below refer to the number(s) on the diagnostic table.



1.This step will make sure OBD system check is performed.
2.This step will make sure there are no other DTCs stored that will affect the operation of the glow plug system.
3.This step will check each glow plug for an open.
4.This step will check each glow plug feed circuit for an open.

Attached Images

	glowplug1.gif (28.5 KB, 42 views)
	glowplug2.gif (28.7 KB, 43 views)

woody35. i will check those things when i tomorrow. i looked @ the 1st pic of the diag, and not sure if i can do that since i can't even access the ECU with an scan tool.

its going to be pretty hard to diagnose without one

yea, i know. every time i plug the scan tool in, i just get, "can't connect to the computer, try again"

Did the fuse for aux cig ligther circuit.

The OBD II connector is powered by the aux cig ligther circuit.
If fuse is blown scanner will not read the puter

here is a schematic also

Attached Images

12.jpg (23.0 KB, 41 views)

got to check the wires running in and out of the puter for breaks