ACC / B0421 01

Read the instructions below then start the fault diagnostic procedure.

Symptom: Defective temperature control.

B0421 01

Fault symptom

Defective temperature control.

On-board diagnosis

Type of diagnosis:

Continuous

Enable criteria:

Ignition ON.

Output activated.

Fault criteria:

Short-circuit to B+ or high current consumption in the circuit of the mixed air damper motor.

System reaction to a fault:

None

Checking the wiring harness

Move the wiring harness at several spots and in several directions to reveal intermittent breaks and short-circuits. Check switches, connectors and crimp connections for oxidation, retracted pins and pin clamping force.

Diagnostic help

Diagnosis regards:

Electrical fault in connecting leads or component.

Functions in the diagnostic tool related to the fault:

Test value:

Air Mix Door Motor Right

Activation:

Air Mix Right

(See also description of readings/activations in diagnostic tool)