Alfa Romeo Forums banner

1 - 6 of 6 Posts

·
Registered
Joined
·
4,501 Posts
Discussion Starter · #1 ·
So, I did a search for this one and ran across some speed-sensor fault subjects here on the BB... Is that basically what the 1252 code means - an issue with the speedometer input to the ECU/dash? (From the dash to the ECU or vice-a-versa?) Or is this the ECU saying that there is no signal to it period?

Does the signal come from the tranny on these cars to the ECU and it distributes the signal to the cluster, or is there a seperate input to the instrument cluster from the tranny and it provides feedback to the ECU for "coordination" with the dash and with the ABS functions?

Me thinks (this is on the 6-speed manual converted - ex-automatic - car), since I have not yet sorted the speedometer after the conversion, this is the reason that I am getting this fault-code, no...? There is an associated early ABS activation sensed in the pedal (even in dry weather), that may be the ultimate result of not having the proper wheel-speed input?

So, I wonder how I would go about feeding both the ECU the signal as well as the dash, or would the ECU provide the proper signal to the dash, once I bring it to the ECU...?
 

·
Premium Member
Joined
·
9,873 Posts
So, I did a search for this one and ran across some speed-sensor fault subjects here on the BB... Is that basically what the 1252 code means - an issue with the speedometer input to the ECU/dash? (From the dash to the ECU or vice-a-versa?) Or is this the ECU saying that there is no signal to it period?

I will try to help here jj, Yes, that would be my guess. Especially if you changed out the cluster.
I would say there is signal just not correct.


Does the signal come from the tranny on these cars to the ECU and it distributes the signal to the cluster, or is there a seperate input to the instrument cluster from the tranny and it provides feedback to the ECU for "coordination" with the dash and with the ABS functions?
The signal does come off the transmission, sensor located kind of under the dip stick on the rear. It is a direct line into the cluster, the cluster pretty much does all the work here in translating the signal
The cluster panel receives the instantaneous speed and reference signals from the speed sensor L17, on pins 9D & 16D
The information signal is used to pilot the onboard speedometer; furthermore the corresponding signal, after being adapted and amplified by the instrument panel internal circuits, is distributed to a series of systems requiring this type of signal (i.e injection and igintion systems, electronic auto transmission, cruise, etc)

Me thinks (this is on the 6-speed manual converted - ex-automatic - car), since I have not yet sorted the speedometer after the conversion, this is the reason that I am getting this fault-code, no...? There is an associated early ABS activation sensed in the pedal (even in dry weather), that may be the ultimate result of not having the proper wheel-speed input?
Most likely the problem. I would convert it to a Manual Cluster, the ABS should not have anything to do with the speedo sensor. The ABS light is directly controlled by the ABS unit.Check for a loose ground, loose sensor, brake switch
So, I wonder how I would go about feeding both the ECU the signal as well as the dash, or would the ECU provide the proper signal to the dash, once I bring it to the ECU...?
Correct cluster, sensor is all you need. Cluster does the rest as stated above. What cluster are you using? the old Auto? You should change it to a Manual one. Let me know? I have one.
And last, do you have a manual with wiring? It comes in handy! ;)

Jason
 

·
Registered
Joined
·
4,501 Posts
Discussion Starter · #3 · (Edited)
Hey thanks - yeah - I referenced the 6-speed converted 3.45 litre car because there is a GREAT deal more detail there! I'll recap here...

In summary;
1) The car WAS a 1995 US spec automatic 164 LS (Super)...
2) I converted the pedal-box, master, slave, clutch, throw-out etc to the manual parts from a 5-speed 164.
3) Installed a 6-speed manual gearbox from a South African 156 GTA.
4) As far as I know, there is NO speed signal-generator on those 156 gearboxes - they take-off wheel-speed from the ABS wheel-sensors, no?
5) Consequently, there is NO speed-signal hooked up on the my car currently.
6) Installed the instrument cluster from a 1994 European model manual 164 Q.

Again, the speedometer input plug coming from the car's main harness in the engine-bay (that would normally hook up to the tranny), is not connected at this stage.
 

·
Moderator
1991 164L
Joined
·
27,634 Posts
Since you are plowing new ground with this 6-speed conversion that does not have a speedo sender like 164 had the 1252 code is almost meaningless since car no longer an automatic. However, the speedo signal is needed to trick the ABS and cruise control systems into thinking the car is moving and of course to get a speedo reading.

Also you need to/ should have the safety switch for cruise control on clutch pedal and hooked up to same circuit as brake pedal switch for disengaging CC.

Did you ever figure out what kind of sin wave or whatever the 156 ABS sensors send to speedo?

On the 24v 164 the speedo sender in tranny differential case gets power from instrument cluster and then sends signal to instrument cluster to run speedo and further send signals to motronic ECU, tranny ECU, ABS and cruise control systems see page 381 in 94 wiring diagrams.
 
1 - 6 of 6 Posts
Top