Motronic M1.7 code "1252"

AlfaRacer75 · #1 (**permalink**) 01-17-2005, 08:59 PM

On my 24 valve Milano (Motronic M1.7) I'm getting the error code 1252. The manual lists this as "Speed sensor faulty". Any idea what this is? Does the ECU read actual vehicle speed? It's not ENGINE speed, because that comes from the crank or cam angle sensors.

Any idea why the Motronic ECU wants to know vehicle speed? Is there an electronic speed limiter? If I reset the ECU the code goes away temporarily, but once I go out and romp on the car a bit it always comes back. Engine seems to be running fine... so pretty sure it's not in "limp home" mode or anything.

75evo · #2 (**permalink**) 01-17-2005, 10:21 PM

1252? Sounds ghey.

Maybe it is the crank sensor. That is the only thing which measures speed. The cam sensor is for determining the phase.

AlfaRacer75 · #3 (**permalink**) 01-17-2005, 10:24 PM

Nope, crank angle sensor has it's own error code. And as far as I know the engine won't start if the crank angle isn't working...

turbolarespider · #4 (**permalink**) 01-18-2005, 07:55 AM

Chip
There are a handful of reasons why a modern ECU would want vehicle speed, some to estimate gear, some to help with the idle control system, some for speed limiting.

I doubt that the car would start "limping" home w/o a speed sensor- there are a bunch others that it would start doing odd things, though.

Eric

BlackAlfa · #5 (**permalink**) 01-18-2005, 08:23 AM

Somebody is spying on how fast you are driving

...

On the 164, there is a connection from Motronic pin 73 to speedometer at the instrument panel. This signal is likely used by the CAE (automatic transmission). Probably not important for your Milano - until you move that automatic over also

!

Bob

Mottic · #6 (**permalink**) 01-18-2005, 02:39 PM

Without being an expert on M1.7, I might suggest that it could be searching for a wheel speed signal. It's a necessary input for present day ABS, so I wouldn't be surprised if that were also the case on facelifted 164s.

Someone with a manual could look at the pinpoint test for 1252 and tell us what system we're looking at..

Again, just a guess.

AR4me · #7 (**permalink**) 01-18-2005, 04:17 PM

Chip,

Did you try asking on the 164-board?

Jes

Mottic · #8 (**permalink**) 01-18-2005, 06:47 PM

I'd tell him the same thing over there

In all seriousness, Steve may know.

**Alfisto Steve** · #9 (**permalink**) 01-18-2005, 06:53 PM

Pin 73 (gry-blk wire) on Motronic ECU receives speedometer signal through connector G154 pin 3 to gray wire coming from intrument cluster connector 2Di connector on 24v 164. The 1252 fault code probably for that (missing) signal. Pin 2Di goes to speedometer signal amp inside instrument cluster.

AlfaRacer75 · #10 (**permalink**) 01-18-2005, 06:56 PM

I know the Automatic transmission cars have a different harness, and it interfaces with the ecu for the trans. Are the ECUs the same? I know for a fact that I have a harness and ECU from a manual car.

Does anybody have the 164 manual? According to the list of error codes on the 164 website, it says to do test N. I don't have the manual so I don't know what test N is...

I figured it has something to do with either a speed limiter or possibly to let the ECU know which gear the car is in... Just wondering if the fact that it's missing in my engine-swap will cause any problem.

Like I said, it's running good... actually it hauls arse.

**Alfisto Steve** · #11 (**permalink**) 01-18-2005, 07:08 PM

Test N is for testing that speedometer works and checking that wiring is OK. If speedo doesn't work on 164 24v it says fix circuits and if wiring is good to ECU change ECU.

Don't think you have a problem with ECU just missing signal from speedo.

Mottic · #12 (**permalink**) 01-18-2005, 07:18 PM

In that case, I can't think of anything that would use that signal besides the A/T on those cars. I would assume that you've been getting this code ever since the install and that it is not a new development?

AlfaRacer75 · #13 (**permalink**) 01-18-2005, 07:20 PM

Thanks Steve.

Guess I'll just ignore the code for now, probably switch to some sort of programmable F.I. later this year anyway.

I'm assuming that the signal from my Milano speedometer will be nowhere near what the ECU is expecting...

AlfaRacer75 · #14 (**permalink**) 01-18-2005, 07:22 PM

Quote:

Originally Posted by Mottic

In that case, I can't think of anything that would use that signal besides the A/T on those cars. I would assume that you've been getting this code ever since the install and that it is not a new development?

75evo · #15 (**permalink**) 01-18-2005, 08:16 PM

Chip,

Do you want Autronic? LordAlfa was selling his Autronic SM2 for $800ish. Came of his 164S Turbo. Plug and play. Maybe even with teh proper crank pulley. Actually Patpend2000 has his SMC up for sale. Completed harness. Reasonably priced too.