General 155 HGT ECU - Help needed

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General 155 HGT ECU - Help needed


New member
Aug 18, 2007

Continuing with my HGT lacking power thread, I took my car to a local garage for diagnostics checking. The garage is a Bosch specialist but could not connect to the HGT ECU. The garage can test the Bosch Motronic M2.10.4 (147 HGT ECU?). Few questions:

1) Is the 155 HGT ECU a Bosch Motronic ME3.1?
2) Is the connector the 3 pin?
3) Where is the connector?
4) Can only a Fiat dealer connect to the 155 ECU?

Any help is greatly appreciated as myself and the garage are stumped on this one. :confused:


If the garage is genuinly a real Bosch specialist, they should have all the information to find out how to communicate with the ECU.

In any case everything needed is written on the ECU itself.

I am not trying to be patronising but my gut feeling tells me to run fast.
on an early 155 you need to use the 3 pin connector (which one depends on the module you want to access), on a later (2001) 155 you need to use the obdII connector.

the 3 pin connector will be attached to the engine bay fusebox cover. i think the obdII connector is under the steering column.
I have found 3 3-pin connectors attached to the fuse box. One has 2 black wires and the others only have 2 wires as well. Is it one of these or should the connector have 3 wires going to it?

There is no OBD2 plug under the dash so I assume it is one of the 3-pins in the engine bay?
There is a 3 pin connector above the passenger footwell, this one has three wires going to it (black, green and Orange/White). Is this the diagnostic connector?
the 3 pin connector to use for main ecu diagnosis has 3 wires, i've always seen the signal ground as black and the k-line as white, the third is always the earth to use for the obd reader but colour can vary. then you need a seperate live from the battery to the obd reader.

in your case i would think the green is earth (pin4 on obd reader), the black is signal earth (pin5 on obd reader) and the orange/white is the k-line (pin7 on obd reader). the live from the battery needs to go to pin16 on obd reader.

i'm not sure if the connector you've found is for the main ecu or the airbag or the abs, there's only 1 way to find out.
if any of the other 3 pin conectors with only 2 wires have a black and a white wire then use that connector. you'll need to give the obd reader a seperate live and also an earth using the battery and chassis.
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