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Obd2 Code P1618 Still Won't Go Away

Question

Posted

I posted a month ago on this problem (jumping in a bit late)...

http://volvospeed.com/vs_forum/index.php?s...92&hl=p1618

and after the car began showing other ABS symptoms (ABS light, flashing UP arrow, etc) I ordered a rebuilt ABS from Victor.

Received the rebuilt ABS from Victor yesterday - easy installation, followed instructions, car w/new ABS runs quick "test" at 14 mph as advertised - but the CEL still stays on. Code reader gives me back my old friend P1618. Clear the code and it comes right back, within seconds of starting the car.

So - what I guess I've got is a multi-symptom / multi-cause problem which has been partially fixed by installing the rebuilt ABS.

Returning to my original hypothesis on this - several old posts have listed the description for P1618 as:

P1618 VOLVO Cable fault between AW 50-Q2 TCM and Motronic 4.4 ECM (MIL lamp lights)

or

P1618 VOLVO Fault in Lead Between AW 50-52 and Motronic 4.3 (MIL Requested)

which translates loosely as: "Broken Wire" or "Dirty connector"

MY QUESTION(s):

Does anyone know where the cable/connector(s) between these units are?

How about a Pin-out on these connectors?

Thanks - anything but a trip to the dealers - (please!)

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12 answers to this question

Posted

I believe the ECU and TCM are both located in a plastic box behind the passenger headlight. You can pull them out and clean the connectors.

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Posted

OK - a quick self bump -

Both ECU and TCM modules removed, contacts cleaned and units replaced. Original ABS unit sent back to Victor for analysis -

Meanwhile - the other description I've found for code P1618 is:

" the TCM has kindly asked the ECU to turn on the CEL because it has detected a fault in the transmission and can't turn it on by itself"

or something like that. So - is this an alternate diagnosis or can one fault code mean 2 different things? One would hope that with all the numbers available they could spread things out and not have to double up...

On the off-chance that this may still be a cable problem I'm asking (again) - does anyone have a wiring diagram of the connector(s) between ECU, TCM, and ABS? I know it was on this forum (or as a maintenance question) abou 3 years ago.... anybody?

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Posted

What's the year/model and transmission of your car?

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Posted

not quite sure, but i do know that if the abs is still acting up it will throw tranny codes.. "safe mode" and changes the shifting habits of the car.. i had mine get stuck in 3rd and 4 th gear..

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Posted

Car is '99 V70XC auto (have to check tranny & control unit model #s )....110K miles.

So far the "usual" ABS symptoms I was getting before (flashing UP arrow, ABS light, other CEL P-codes) have not returned since I replaced the ABS module with a rebuilt one from Victor, but the P1618 code/CEL is solid.

Thanks...

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Posted

Check your messages... hope the diagrams help somehow.

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Posted

have you cleared codes from the TCM and ECM?

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Posted

Thanks to evilb - the diagrams were exactly what I was looking for....no more wiggling wires in the dark.

I've been reading and clearing the CEL and codes with my (generic) OBDII reader - don't know of any (non-dealer) method for clearing TCM codes...is there a way? I'll check these diagrams - maybe there's a "clear" terminal somewhere...

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Posted

Victor is very good and should work through this with you if he isn't already?

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Posted

there isnt....

i have had cars in the past that would not clear that code with a generic scantool, but using a good scantool would clear the codes in the TCM and no more problems...

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Posted

just hit up pep boys or advanced and get them to use one of the expensive ones.

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Posted

Resurection of an old post.

Has there been any positive new info on this nasty code?

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