Test Notes

Output Functions

Glow Plug Relay - A relay that controls the current flow to the glow plugs. Glow plug relay ON time is controlled by the Powertrain Control Module (PCM) and is a function of engine oil temperature, barometric pressure and battery voltage. Glow plug ON time normally varies between 10 to 120 seconds.

NOTE: WAIT TO START lamp ON time is independent from glow plug relay ON time (1 to 10 seconds).

Detection/Management
An open or shorted to ground glow plug relay or WAIT TO START lamp circuit can be detected by an on-demand output circuit check performed during the KOEO standard test.

On all 49 state non-OBD II vehicles, glow plug and glow plug harness concerns cannot be detected by the PCM.

CAUTION: Do not perform any voltage checks with the engine running; 115v DC at 10 amps present on injector circuits.

Enter this pinpoint test only when directed here from the symptom flowcharts.

This pinpoint test is intended to diagnose only the following:
- Powertrain Control Module (PCM)
- harness circuit: GP/RELAY coil
- glow plug relay coil

Description

Glow Plug Monitoring System for California OBD II
The glow plug system is monitored when the glow plugs are commanded on for more than 35 seconds (Engine Oil Temperature (EOT) needs to be below 49°C [120 °F])and battery voltage is between 11.8-14 volts for 1998 or 11.5-14 volts for 1998-1/2 Econoline and 1999 F-Series.

You can monitor glow plug amperage using NGS PIDs GPMR and GPML.

DTC P1395 or P1396 will set on the bank that is reading less than 32 amps or the bank that is reading at least 8-1/2 amps lower than the other bank. Loose fitting pins in the circuit connectors causing high resistance or high resistance glow plug(s) on that bank could be the cause. A shorted circuit or low-resistance glow plug(s) on the opposite bank could also be the cause. Each bank needs to draw more than 32 amps but not more than 8-1/2 amps apart.

DTC P1391 or P1393 will set when the monitor indicates that all four glow plugs are not being powered on the bank. An open in the glow plug circuits, glow plug relay, glow plugs or monitoring circuit could be the possible causes.

Both DTCs P1391 and P1393 together will set when the monitor indicates that all eight glow plugs are not being powered. An open in all glow plug circuits, the glow plug relay, glow plugs, fusible links or all three monitoring circuits could be the possible causes. If KOEO On-Demand Self Test DTC P0380 is also set, a concern on the glow plug relay triggering circuit will cause all three DTCs to set.

NOTE: Look very carefully for poor connections, burnt looking or loose fitting pins that will cause high resistance and set a code.

The Glow Plug Monitor Self Test (California only) is a functional test of the Powertrain Control Module performed on demand with the engine running and the A/C off. For 1998 Econoline, battery voltage must be between 11.8-14 volts to complete the test. It may be necessary to raise engine rpm to maintain battery voltage. For 1998-1/2 Econoline and 1999 F-Series, the test will raise engine speed to 1200 rpm to maintain a system voltage of 11.5-14 V. The PCM will activate the glow plug relay and monitor the glow plug circuits. A fault must be present at the time of testing for the test to detect a fault. If one bank is reading less than 32 amps or one bank is reading at least 8-1/2 amps lower than the other bank, a fault will be detected and a Diagnostic Trouble Code (DTC) will be output on the data link at the end of the test when requested by a scan tool. Only a hard fault code (DTC) will be displayed.

Both California and 49 State
The glow plug on time is dependent on oil temperature and altitude. The glow plug relay comes on between 1-120 seconds and does not come on at all if oil temperature is above 86°F for Econoline or 131°F for F-Series. Using the NGS, you can run the Output State Self Test, which will cycle the glow plug relay on for 5 seconds the first time only that the accelerator pedal is pressed. This Self Test does not set any codes.

You can verify glow plug on time (and amps for California) by monitoring New Generation Star (NGS) tester PIDs EOT and GPCTM (California: GPMR and GPML). The Wait to Start lamp ON time (1-10 seconds) is independent from glow plug relay ON time.

NOTE: Add 5 seconds to glow plug on time when above 7000 feet In altitude, but not to exceed 120 seconds.

DTC Description
P0380 = Glow plug circuit malfunction
P1391 = 4 glow plugs open right bank (California only)
P1392 = Glow plug circuit high input bank No. 1 (right) (California only)
P1393 = 4 glow plugs open left bank (California only)
P1394 = Glow plug circuit high input bank No. 2 (left) (California only)
P1395 = 1-3 glow plugs open right bank (California only)
P1396 = 1-3 glow plugs open left bank (California only)
P1397 = System voltage out of self-test range (California only)
P1389 = Glow plug high side out of range low (center) (California only)