Looking for some accurate information on M104 harness differences

[Jeaton4130]

Need some help identifying the differences between the early and late style 124 m104 HFM engine harness. I have a early harness with 2 pin coolant temp connector id like to modify it into a later 4pin temp sensor type harness. Any information would be sincerely appreiceated. Please and thank you.

95 e320 ASR new ETA, E-GAS ASR Cruise Control Unit, lower harness, rebuilt trans, replaced head gasket/rebuilt cylinder head, found a updated engine harness at the junkyard but its the early 94/95 engine harness and i have later style.

 

[kubasz]

The 2pin temp sensor on early HFM cars /which is part of the AC system i think/ was later moved to the 4pin sensor housing and occupies pins 2 and 3. Pins 1 and 4 are for the HFM control module.

 

[gsxr]

@kubasz - is the temp sensor the only difference between the harnesses? Everything else is the same?

Sounds like it may be easier to convert a late (4-wire) harness to work on an early (2-wire) car/sensor, but the opposite may be more difficult.

 

[captruff]

I think I have a used earlier harness available Part#124 440 56 32 with a manf date? FD 18.11.98

Jeff

 

[kubasz]

On the injection (output) branch of the harness the temp sensor is the only difference between early harnesses (124 545…..) (124 543…..) and later harnesses ( 124 440 ……).

The sensor branch is the part that really is different and:

1. The knock sensors on early harnesses are handled by one common plug and on later cars there are seperate coaxial cables that run to the sensors. The connectors for later sensors are similar to the injector connectors.​

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2. IAT connector is different between 124 545.... and 124 440.... harnesses.​

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3. Crank position sensor connectors are also different between the two types of harnesses and also the plugs are split from the main branch in different spots. The 124 440.... crank sensor connector is the same as for the cam position sensor.​

I can attach pics for early and later harnesses tomorrow if anyone is interested.

 

[kubasz]

I would like to correct myself with the early part number for injector harnesses. After checking my notes its 124 543 .... , not 124 545 ....

 

[Jeaton4130]

Thanks for the information.
Focusing on specifically the later style harness and its 4 pin temp connector...
I think two of the four wires travel directly to the ecu connector and the other two wires are somewhere connected to the HVAC system. Where and what connector on the engine harness is connected to the HVAC system? I appreciate any information y'all can share. Thanks