GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2002 🢒 Chevy C Cab/Chassis HD (GMT 400) 🢒 Engine 🢒 Engine Controls - 6.5L 🢒 Glow Plug System Diagnosis

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 powertrain control module (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 the glow plugs. When the 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, the 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

The numbers below refer to the numbers on the diagnostic table.

  1. This step will make sure the Diagnostic System Check-Engine Controls is performed.

    2.

  2. This step will make sure there are no other DTCs stored that will affect the operation of the glow plug system.

    3.

  3. This step will check each glow plug for an open.

    4.

  4. This step will check each glow plug feed circuit for an open.

Step

Action

Yes

No

1

Important: Before clearing DTCs use the scan tool Capture Info to record Freeze Frame/Failure Records for reference, as data will be lost when Clear Info function is used.

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Is DTC PO117, PO118, or PO380 stored as history or current codes?

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect all the glow plugs.
  3. With a test lamp connected to B+, probe the spade terminal on each glow plug.

Do all glow plugs illuminate the test lamp?

Go to Step 4

Go to Step 9

4

  1. Turn ON the ignition with the engine OFF.
  2. Verify the glow plugs are still disconnected.
  3. With a test lamp, jumper each glow plug connector terminal to ground.
  4. With a scan tool, command the glow plugs ON.

Does each circuit illuminate the test lamp?

Go to Step 5

Go to Step 10

5

Does the test lamp stay illuminated all the time for each glow plug terminal (even when the glow plugs aren't commanded ON)?

Go to Step 6

Go to Step 11

6
  1. Disconnect the glow plug output (gray) cable from the glow plug relay.
  2. Probe each glow plug terminal with a test lamp connected to ground.

Is the test lamp illuminated for all terminals?

Go to Step 7

Go to Step 8

7

Repair the short to voltage on the glow plug output circuit or the short to voltage on the glow plug signal circuit.

Did you complete the repair?

Go to Step 11

--

8

Replace the glow plug relay. Refer to Glow Plug Relay Replacement .

Did you complete the replacement?

Go to Step 11

--

9

Replace all glow plugs that do not illuminate the test lamp. Refer to Glow Plug Replacement - Bank 1 or Glow Plug Replacement - Bank 2 .

Did you complete the replacement?

Go to Step 11

--

10

Repair open in each circuit that does not illuminate the test lamp?

Did you complete the repair?

Go to Step 11

--

11

Operate vehicle within the conditions under which problem was noted.

Does system operate properly?

System OK

Go to Step 1