DTC 4-1-8

DTC 4-1-8. NO CONTROL SIGNAL TO POWER STAGE:





- Condition for DTC:
If there is no control signal to the passenger compartment fan power stage, the control module records the fault and stores the DTC.

- Cause of fault:
Open circuit in wire between control module and passenger compartment fan power stage or internal fault in passenger compartment fan power stage.

- Symptoms:
Fault warning to driver. LEDs by A/C and REC buttons flash for 20 sec. Control module substitutes a preset value of 4 V equivalent to a 28 % speed setting on the passenger compartment fan.

Connect Test Unit To Control Module:





- Ignition off.
- Connect test unit between control module and A/C system connector and check GND points. Connecting and Disconnecting Test Unit
- Go to the next step "Check Control Signal To Power Stage".

Check Control Signal To Power Stage:








- Ignition on.
- Fan switch in manual setting equivalent to max. speed.
- Connect a voltmeter across # 6 (0 V) and # 42. Voltmeter should read approx. 6-8 V.
- If value is OK, go to the next step "Check Resistance Of Control Signal Wire".
- If value is not OK, if voltmeter reads 0 V, wire is shorted to 0 V.
- If voltmeter reads 12 V, wire is shorted to 12 V.
Check wire between wire connector pin 1 A and connector B pin B:12 to control module for short. Checking Wires
Rectify short.
Check DTC. Test Procedures

Check Resistance Of Control Signal Wire:





- Ignition off.
- Disconnect the 4-pin connector from power stage.
- Connect an ohmmeter across # 42 and wire connector pin 1A.
- If value is OK, ohmmeter should read 0 ohm.
- If value is not OK, if resistance is infinite, there is an open circuit in the wire. Check wire between connector pin 1A and connector B pin B:12 to control module for open circuit. Checking Wires
Rectify open circuit.
Check DTC. Test Procedures