PROHEAT M-SERIES SERVICE MANUAL
3-27
VOLTAGE: Step 2
(5 Flashes)
OVERHEAT Diagnostic Code
Indicates that the Temperature Sensor detected an inner heat exchanger
surface temperature of 230°F (110°C) within 60 seconds after entering
Cool Down.
Troubleshoot the Overheat diagnostic code based on:
1. Lack of coolant, air or flow problems in the coolant system.
Go to page 3-25, Steps 1 and 2.
2. Faulty Temperature Sensor. Go to page 3-29.
3. Faulty PCM Temperature Sensor circuit. Go to page 3-29.
To reset the PROHEAT, switch it off and then on again.
VOLTAGE Diagnostic Code
Indicates that the supply voltage to the PCM is outside the operating range.
Operating Range:
• 12 volt PROHEAT – 10 to 15 volts.
• 24 volt PROHEAT – 20 to 30 volts.
Troubleshoot the Voltage diagnostic code based on:
1. Low voltage.
• Voltage supply is below the rated requirement.
• Poor or faulty electrical connections.
• Voltage supply source is OK. Voltage drop due to high amperage load
while the PROHEAT is operating or trying to operate.
2. High voltage.
• Voltage supply is above the rated requirement while the vehicle
engine is running.
High Voltage – Check:
The vehicle charging system. Consult the OEM for service requirements.
Low Voltage – Check:
a) System voltage supply source.
b) Wiring harnesses and connection points.
3.1.4
(4 Flashes)
3.1.5
(5 Flashes)
VOLTAGE: Step 1
(5 Flashes)
CAUTION
Repeatedly resetting the PROHEAT
without resolving the Overheat
diagnostic code will damage the
heat exchanger.
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