U1170

20AA04 - U1170

Information saved in
DME

Fault code
20AA04 - U1170

Fault text
Coolant pump, communication: malfunction

Fault description
The diagnostic function monitors BSD bus communications
with the electric water pump.

Condition for fault identification
Test condition:
The fault is recognized when the electric water pump fails to
respond to BSD bus messages from the DME.
Potential problem source(s):
- Defect in wiring harness to water pump
- Communications problem on BSD bus
- Defective water pump
Terminal condition: Terminal 15
Voltage condition:
- Onboard electrical system voltage between 9 V and 16 V
Temperature condition:
- None
Time condition:
- None
Other conditions:
- Engine on
- No BSD fault

Condition for fault memory entry
The diagnostic fault code is logged when the fault remains
present for longer than 1 min.

Action in service
- Continue test routine with test modules that deal with
problems related to voltage in onboard electrical system
- Check wiring harness between water pump and DME
- Conduct tester job
- Replace water pump

Fault effect and breakdown warning
Breakdown notice:
None
Possible apparent symptoms:
Breakdown in extreme cases, electric water pump stops
operating - engine overheats

Driver information
Warning light:
- ECE emissions warning lamp: off
- ECE electronic engine power reduction: off
- CC message: on
- US emissions warning lamp: off
- US electronic engine power reduction: off
- CC message: on

Service instruction
Observe sequence for fault rectification:
- If the pump is activated at TMOT>90 °C as tester job the
diagnostic fault code 0x3792 or 0x20AD08 'Water pump:
rotation speed implausible' can be logged, ignore this fault
and delete it --> Carry out tester job at Tmot<90 °C