What does it mean?
B1621 is a Body (airbags, seat belts, body electronics) fault code. It indicates: ECU Hardware Error .
Symptoms
- Rear wiper does not park and stops wherever it happens to be when switched off
- Wiper keeps sweeping after the switch has been turned off
- Rear wiper fuse blows repeatedly
- Blade stalls against the trim or the glass surround and the motor strains audibly
- On the hardware fault variant, several unrelated body functions fail and the module may not answer the scan tool
Likely causes
- Park position wire chafed against a powered circuit inside the tailgate
- Water inside the rear wiper motor housing bridging the park contacts to the supply
- Wiper motor park switch shorted internally
- Aftermarket wiring in the tailgate area, such as a camera or extra lighting, back-feeding the circuit
- Connector terminal displaced onto a powered pin
- Module input clamp damaged by the short
- On applications where this code reports an internal fault, a hardware failure inside the control module itself
How to fix it
- With the wiper switched off, measure the limit input at the module and again at the motor, looking for battery voltage where there should be none
- Unplug the motor and repeat the measurement to separate the motor from the harness
- Open the tailgate hinge conduit and inspect the loom for chafe and moisture, since both are common there
- Check the wiper motor housing for water, rust and corroded park contacts
- Disconnect any aftermarket tailgate wiring and retest
- Repair the harness and replace the motor if its park switch measures shorted
- On the hardware fault variant, verify module supply, ground and software level, then follow the manufacturer procedure before replacing the module