wee bit of help please?

marty

Member +
Went for a Sunday spin today up the coast and car seemed to be running fine..then looked down and noticed my speedo wasn't working. I thought maybe the speedo cable was wrecked or something so not to much to worry about hopefully.

Then about an hour after that was overtaking and just got pulled back into my own lane and saw the engine light was on. So pulled over to the side of the road and switched the car off and on again and that solved it. As I pulled away and got a bit of speed up it came on again and will continue in this cycle of being off when you first start the car and coming on when you get up to speed..

Is a diagnostic check my first port of call or where do I start?

Cheers

Marty
 

dac69er

Super Moderator
if the ecu doesnt see a vehicle speed it puts the engine light on. you can do a fault code test, but will most likely tell you what you already know!

replace the cable, or find what the problem is with it and you will be fine again!
 

marty

Member +
if the ecu doesnt see a vehicle speed it puts the engine light on. you can do a fault code test, but will most likely tell you what you already know!

replace the cable, or find what the problem is with it and you will be fine again!

I see what you're saying but if the ECU didn't see a vehicle speed then would it not have thrown the light on right away?
 

dac69er

Super Moderator
Nope. That is 100% the problem mate. I don't know exactly what it looks for, but I imagine it looks for the engine to be under some load for a designated period of time before it decides to throw the light on
 

marty

Member +
Nope. That is 100% the problem mate. I don't know exactly what it looks for, but I imagine it looks for the engine to be under some load for a designated period of time before it decides to throw the light on
Ahh right. Sounds logical enough to me..so it's probably just the speedo cable I need then? Hope they're not hard to get hold of!!
 

Kyle_R

Member +
its not a live feed ecu as such its more of a pulse system scanning for faults at intervals im lead to believe.(do not know if thats correct just what i was told) so it could take any amount of time for the fault to be seen as apose to instantly noticing it.
 

Texx

Admin
Code 42 states no speed signal detection for 8 seconds with the engine between 2500-5000rpm, I would also expect that the IDL switch in the TPS would need to be open and the PIM voltage from the MAP sensor to be 2.5v or above before the ECU would store code 42.

Basically, you'd need to be driving the car at a steady speed for at least 8 seconds before the ECU would put the check light on.
 

weeJohn

Lifer
Fault code 42, VSS comes up when no speed pulses are being sent from the speedo to the ecu for more than 2 seconds when the engine revs are above 3500 rpm, or something stupid like that.
 

marty

Member +
Right I see now, it's possible the light came on before I noticed it so that makes sense. Got to run a diagnostics anyway as I'm yet to do one on the car. I'll check back when I know more..cheers
 
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