Bmw sib 12-15-05
 

Does anyone have at BMW sib 12-15-05 relating to code P0128 and a possible engine wire harness replacement?


Thanks

I don't have the full SIB but this is the jist of the sib:
10032990 / SIB-12-15-05 | The Center for Autosafety

Before you look at the engine coolant or actual wiring harness, however, check your thermostat heater coil. The coil is activated by the engine during warmup to accelerate the opening of the thermostat.

You didn't list which model you have, but I assume you have a wire harness running to and connecting into the thermostat. Disconnect that harness and you should see two brass conductors exposed in the connection point on the thermostat. Measure the resistance between those two conductors using a multimeter and it should read between 14 and 16 ohms. If you get a reading of 1, or infinity, then the thermostat heater coil has burned open.

The thermostat will still operate properly in reaction to water temperature. The engine runs a diagnostic program on start up to check the circuit for this heater coil. If it is absent in the circuit you will get the SES light with the P0128 code. To remove the SES light and fault you will need to replace the thermostat, which including draining coolant, removing hoses and replacing the thermostat is about an hour DIY job.

If the heater coil is intact then you may indeed have a break in the harness or another problem and will need to continue troubleshooting.