Section 00-00: Power Stroke Diesel Engine | 97-15A 7.3L DI Turbo Workshop Manual |
ELECTRONIC CONTROL SYSTEM DIAGNOSTICS |
Output Functions
Glow Plug Relay
Controls the current flow to the glow plugs. Glow plug relay "ON" time is controlled by the PCM and is a function of engine oil temperature, barometric pressure and battery voltage. "ON" time normally varies between 10 to 120 seconds. The glow plugs are self-limiting glow plugs and do not require cycling on and off. (The glow plug relay will only cycle on and off repeatedly when there is a system voltage condition greater than 14.5 volts.)
Glow Plug Wait to Start Lamp
Lamp that indicates to the operator when the glow plugs have been on long enough to crank the engine. It is controlled by the PCM. Wait to Start lamp "ON" time is a function of engine oil temperature, barometric pressure and battery voltage. "ON" time normally varies between 1 to 10 seconds. (NOTE: Wait to Start lamp "ON" time is independent from glow plug relay on time.)
Fault Detection/Management
An open or shorted to ground glow plug relay in the control side (coil) or Wait to Start lamp circuit can be detected by an on demand output circuit check performed during the Engine Off Tests.
The glow plug relay (power/switch) side, glow plugs and glow plug harness problems can not be detected by the PCM.
Test Points | Spec | Comments |
---|---|---|
B+ terminal to ground | B+ | Relay switch power, B+ should be present at all times (terminal with single 6 gauge wire). Check connection at starter or fusible links if no power (voltage) present. |
Glow Plug Feed to Grd. | B+ | Glow plug feed voltage should be present 10 to 120 seconds after key is cycled on, dependent upon battery voltage, barometric pressure (altitude) and engine oil temperature. |
B to Ground | B+ | Relay coil power. Voltage should be present when ign. key is ON - Check fuse if no voltage. |
Pin #101 to Ground | 0v / 12v | Glow plug control, switched to (grd) by PCM during operation. 0v = relay ON, 12v = relay off. |
Test Points | Relay to Harness Connector | Comments | |
---|---|---|---|
Glow Plug Number | Pigtail Connector to Ground (B-) | ||
Spec | < .1 to 2 ohms | < 6 ohms | Relay to Harness Connector NOTE: All engine harness connectors for glow plug/injectors should be disconnected before taking measurements. High resistance could indicate an open circuit in the engine harness between the glow plug connector and the relay. |
#1 | Pigtail Connector to Ground B- High resistance could indicate an open circuit in the UVC (under the valve cover) harness or in the glow plug. Glow plug resistance should measure .1 to 2 ohms dependent upon engine temperature. | ||
#3 | |||
#5 | |||
#7 | |||
#2 | |||
#4 | |||
#6 | |||
#8 |
0380 = OCC CHK performed by PCM during engine off test. Indicates high or low resistance in GP relay coil circuit. |
0381 = OCC CHK performed by PCM during engine off test. Indicates high or low resistance in GP lamp circuit. |