Fault Code Guide

Backlighting Circuit Tests
Test Conditions Test Point
Good
Result
What to Do if Test Fails
backlighting
power test
battery switch on (if equipped)
key off, engine off
control head connector
disconnected
headlight switch on
Measure voltage between
pins A2 (positive lead) and
B8 (negative lead) on the
control head connector while
toggling the dimmer switch
between full dim and full
bright.
voltage
should
be
about
1.2V at
full dim
and
10.8V
at full
bright
Check circuit 29A for an open/
short.
If okay, refer to Group 54 for
further diagnosis.
backlighting
pulse width
modulated
(PWM) signal
test
battery switch on (if equipped)
key off, engine off
control head connector
disconnected
headlight switch on
Measure frequency between
pins A2 and B8 on the
control head connector.
400 Hz Check circuit 29A for an open/
short.
If okay, refer to Group 54 for
further diagnosis.
*
The voltage should be approximately the same as the battery voltage.
Table 11, Backlighting Circuit Tests
J1587 Fault Codes, HVAC (bulkhead module related) MID 164
MID SID FMI Fault Description Action
164 057 05 A/C clutch output open circuit (low
current)
Check circuit 98A for an open circuit.
Check binary switch; it may be open. If
open, check for low or high refrigerant
pressure. Also check the switch itself.
Check A/C clutch coil for an open circuit.
06 A/C clutch output shorted to ground (high
current)
Check circuit 98A for a short to ground.
Table 12, J1587 Fault Codes, HVAC (bulkhead module related) MID 164
J1939 Fault Codes, HVAC (bulkhead module related) Source Address (SA) 33
SA SPGN FMI Fault Description Action
33 1550 05 A/C clutch output open circuit (low
current)
Check circuit 98A for an open circuit.
Check binary switch; it may be open. If
open, check for low or high refrigerant
pressure. Also check the switch itself.
Check A/C clutch coil for an open circuit.
06 A/C clutch output shorted to ground (high
current)
Check circuit 98A for a short to ground.
Table 13, J1939 Fault Codes, HVAC (bulkhead module related) Source Address (SA) 33
Cab Heater and Air Conditioner, Valeo 83.00
Troubleshooting
Business Class M2 Workshop Manual, Supplement 13, March 2008300/18