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Ist gear switch question...

1K views 40 replies 7 participants last post by  Jamie C 
#1 ·
Ive had an ECU code keep coming up, was the code for first gear boost cut switch.

Now today i disconnected the switch and no faults anymore but, does the car now think its in 1st all the time as the plug is no longer connected to the switch or will it never register 1st gear? Dont know which way round the switch operates and was too late to check it.

So do i have to bridge the two wires together to make the car think its outta 1st or shall i leave em unconnected from each other?

Ta, Jamie.

:beer:
 
#3 ·
Thanks fella, why would the light come back though?

Thought the code 41 was for low voltage at 1st gear switch, which would indicate poor conductivity or high resistance at switch would it not? Or can it mean no signal?

Thing is ive tested resistance at switch now by putting multimeter on the terms of the switch, i get infinite resistance when in neutral or other gear, in first it shows less than one ohm, which is probably what youd expect.

So if the switch is working fine why would it show a code for it?
 
#5 ·
Might pop out in a min and bridge em, will let ya know what happens.

As long as it dont log a fault im happy, not worried bout loosing boost limiter in 1st, just have to exercise a lil extra caution with the right foot.
 
#6 ·
Right then, bridged the wires together today, popped up a fault code within a min of driving, same one again. :(

Why would it log a code for the wires being bridged? All thats happened is youve made a connection, which is what the switch does anyway!

And if it logs the fault code and ECU light stays on then does it go into boost limiting limp mode?

Ta. :beer:
 
#9 ·
The ecu will throw up a failure after a while if either the wires are shorted together or left open circuit.

It's knows which gear you are in by the revs per MPH so knows the switch isn't working correctly.

If you have a problem on a standard car then first check that the reversing lights are working correctly.

Then check the switch is open circuit when in 1st gear.
 
#10 ·
Thanks Andy, had pondered if it was to do with car knowing you oughta be put of first according to speed.

Does the ECU go into limp mode when senses this fault? ie keeps it at low boost?

Reverse lights are working just fine it would appear, have checked switch as stated, get no circuit when in neutral or other gear, and circuit is made when in first. Is that the right way round for it to work?

ta, Jamie.
 
#12 ·
How could the switch be getting itself @r$e about face like that?

Ill have to recheck it tomorrow see if its me that got it the wrong way round.
 
#15 ·
So ill park the car facing up a very steep slope before removal then.

Any gen on the thread size of 1st gear switch, anyone with EPC? Might say in there.
 
#17 ·
Checked it again today, it was me that giit it @rse about face, get open circuit in 1st and closed in other gears.

I did notice that in 1st you obviously get infinite resistance as no circuit made, if i push it into 2nd from there i get 1ohm (a little resistance expected due to dirty terminals, worn switch, meter leads etc i spose), however if i just knock it back to neutral i get resistance reading jumping up and down in the hundreds of ohms, does this mean the switch may not be re-engaging properly sometimes?

?
 
#21 ·
Aaaaaagh, nnnnooooooooooooooooo!!!!!!!!!!!!!

Fitted new switch today, reset ECU. got bout 2 miles down the road and up blinks the management light. Check the code.......code 41 again!!

Dammit all.

Any more pointers please chaps? :( :( :(
 
#22 ·
its gotta be the wiring then mate. get a pin out diagram from johnA website and check the pins from the ecu plug to the 'box 1st gear switch plug with a meter and see if you have an probs.

rodgerq
 
#23 ·
Cheers rodgerq, thats a whatta im gona havta do, sunday job i reckon.

Disconnected reverse gear switch tonight and drove it like that in the vain hope it may be playing up even though it tested fine, no joy, same ole.
 
#24 ·
Gonna go out and test wiring in a few mins or so but what exactly am i looking for?

Theres obviously not a broken wire cos ECU knows and registers a fault code when wires bridged together, no code when unbridged.

Is the wiring not just straight out from one pin to the switch, then from switch straight back to another pin?
 
#25 ·
Right, bear with me here, im useless with these diagrams (pin out)

I can see the circuit that represents the 1st gear switch and it goes to pin 2 on the ECU, where does the other end go to? Is it a pos or neg circuit, im a little lost :eek:

 
#26 ·
BASStra said:
Checked it again today, it was me that giit it @rse about face, get open circuit in 1st and closed in other gears.

I did notice that in 1st you obviously get infinite resistance as no circuit made, if i push it into 2nd from there i get 1ohm (a little resistance expected due to dirty terminals, worn switch, meter leads etc i spose), however if i just knock it back to neutral i get resistance reading jumping up and down in the hundreds of ohms, does this mean the switch may not be re-engaging properly sometimes?

?

Sounds like your swith contacts have got filthy. Guess it's a sealed unit, so no chance of cleaning them - worth changing it man.
 
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