ECU/Speed sensor question expert required??
Discussion
Following on from one of the other threads with regards problems with the speed sensor. I’ve noted previously that when the Speedo is not working (2% of the time 
, note at this point I’m assuming the problem to be the sensor and not the Speedo itself. The engine will idle erratically and sometimes stall when pulling up to a junction, similar symptoms to a dirty stepper.
I believe that this may be the ECU trying to protect the cats from being poisoned because it doesn’t know the car speed part of the equation for fuelling
.
My problem is in understanding the process that is going on here, with the Hot-wire system the fault memory will log a speed input fault code and the car will behave as above. What I would like to know is when the speed input returns (the other 98% of the time does the mapping in the ECU go back to ‘proper mode’ but still store the fault . I ask this as the erratic idling and stalling goes away but the car seems a little flat, as if it knows there is still a fault . This can be cleared in the short term until the next time if the battery is disconnected resetting the ECU.
How does the ECU work then over to you, shpub/Mark Adams maybe please.
Harry
Btw standard rover/Lucas type hot wire ECU system fitted to the car
, note at this point I’m assuming the problem to be the sensor and not the Speedo itself. The engine will idle erratically and sometimes stall when pulling up to a junction, similar symptoms to a dirty stepper. I believe that this may be the ECU trying to protect the cats from being poisoned because it doesn’t know the car speed part of the equation for fuelling
. My problem is in understanding the process that is going on here
, with the Hot-wire system the fault memory will log a speed input fault code and the car will behave as above. What I would like to know is when the speed input returns (the other 98% of the time does the mapping in the ECU go back to ‘proper mode’ but still store the fault . I ask this as the erratic idling and stalling goes away but the car seems a little flat, as if it knows there is still a fault . This can be cleared in the short term until the next time if the battery is disconnected resetting the ECU. How does the ECU work then
over to you, shpub/Mark Adams maybe please. Harry
Btw standard rover/Lucas type hot wire ECU system fitted to the car
whilst there I unfurled the snakes nest and the ECU has AMR2175 14CUX on it and a Land Rover badge with 400HC written across it in permanent marker. Does this help
Thanks for that, so when you say it does 'self diagnose' does taht mean it'll come's out of 'limp home mode' on restoration of the 'out of spec' input and just logs the fault for later reading .
As I've said it only goes to fault 2% of the time so I can't envisage sitting with a multimeter waiting for it to go
.
If the ansewer is yes then it is just an inconvenience whilst the speedo is not working, if you see what I'm getting at.
If however the fault continues to affect performance even after restoration i'll get it sorted now.
What say thee.
harry
. As I've said it only goes to fault 2% of the time so I can't envisage sitting with a multimeter waiting for it to go
. If the ansewer is yes then it is just an inconvenience whilst the speedo is not working, if you see what I'm getting at.
If however the fault continues to affect performance even after restoration i'll get it sorted now.
What say thee.
harry
David thanks for the offer but its now in with a TVR doctor for a service and MOT....plus anything else 
, I'll see what comes out of it.
I agree with the no two starts seem the same sentiment, sometimes its as tame as a lamb other times it barks when you kiss the throttle, TVRs' who'd ave em eh.
Harry
, I'll see what comes out of it. I agree with the no two starts seem the same sentiment, sometimes its as tame as a lamb other times it barks when you kiss the throttle, TVRs' who'd ave em eh
. Harry
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