Check Engine Preheat Enable Circuit
engine
Description
The Engine Preheat Enable circuit feedback is out of range; the unit gives an alarm only.
Activation Conditions
Trigger On Glow Plug Relay is ON and Relay Feedback Voltage is below Minimum ON Threshold OR Glow Plug Relay is OFF and Relay Feedback Voltage is above Maximum OFF Threshold. Trigger Off If alarm was active when Glow Plug Output was ON, trigger OFF if Output is ON and FET Feedback Voltage is sensed in Active range OR If alarm was active when Glow Plug Output was OFF, trigger OFF if Output is OFF and FET Feedback Voltage is sensed in Inactive range OR Alarm Reset OR Cycle Power
Unit Behavior
Alarm only
Reset Conditions
See manual.
Corrective Actions
1. Verify if condition occurs when glow plug output is ON or OFF a. Check glow plug output status in System Values menu in CabinTech. b. If status is ON, go to step 2 c. If status if OFF, go to step 5 2. Check voltage at glow plug bus with output activity. If voltage is present, go to step 4 (glow plug resistance check). If no voltage, go to step 3 3. Inspect connections at APU J2-2, glow plug bus, and glow plugs. 4. Check glow plug resistance. 5. Check harness resistance from J2-2 to glow plug bus. If output was OFF when alarm occurred, check harness for short to power. 6. Replace module.