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View Full Version : C20LET Fault 21 and idle at 1500rpm.



krobinson
26-07-08, 05:09 PM
Well just when I thought I had my Nova running 100%, the ECU light popped back on.

When started from cold it idles perfect at 1k. When it get's close to running temperature the rev's rise to 1.5k.

I've changed both the ICV and TPS for brand new units.

The ECU light flash's out 21 = TPS voltage high fault.

Any ideas folks?

Keith

krobinson
26-07-08, 09:11 PM
I've now checked the loom and it is mint at the TPS. I've had the ecu off the past 6 hours and i've check the terminals. Started and the fault returns, it idles at about 1100rpm on cold, and rises to 1500rpm when it gets warm.

I've noticed that even when my pipes are quite hot, the temperature gauge in the car isnt rising at all, could the temperature sensor be faulty and thus causing a fault?

I'm baffled at the moment.

Keith

Adam
26-07-08, 09:15 PM
Check the small connection on the thermostat housing for the dash gauge.

The sensor the ecu uses for coolant temp is different to the dash one

krobinson
26-07-08, 09:55 PM
I'm baffled really at this stage, Would plugging the car into Tech 1/2 give any better diagnostic than the paperclip trick?

Keith

krobinson
27-07-08, 11:21 AM
Bttt

Lee
27-07-08, 11:22 AM
I would definately tech 2 it Keith!

Rich
27-07-08, 03:42 PM
tech 1 would give you the definate fault code, and you will be able to check what temp/revs the ecu think its at

krobinson
28-07-08, 12:02 AM
I think it may be the wireing to the TPS, I took the tophat cover off and jiggled the wireing about, the rev's shot up to 2-2.5k and back to 1.5k each time I moved the wires. So i'm going to have to strip it back and see what could be causing it.

Maybe its bare and earthing against something causing the high voltage fault? Hopefully its something easy sorted, i hate wireing!!

mikey14sr
28-07-08, 08:24 AM
Might be an intermittant break in one or more of the wires?

krobinson
28-07-08, 06:09 PM
Might be an intermittant break in one or more of the wires?

Fingers crossed thats all it is.

Geordie-Chris
28-07-08, 07:40 PM
I know the temp gauge and ecu use different sensors for their readings but I'd definitly look into replacing them if you haven't done so already, there only a few quid from Vaux, and coolant temp sensors can cause all sorts of problems.

krobinson
29-07-08, 06:10 PM
Just to update:

It's still starting and idleing at 1k/1100rpm.

Once it warms up (say 2 min's running) the rev's still rise to 1500rpm.

The ECU is showing fault 21 - TPS sensor High voltage. I've replaced the TPS for a brand new vaux one, which made no differance. The Idle control valve is also brand new.

I've checked the gaskets on the inlet etc, and checked all the pipes for air leaks and there's none.

I'm completely stuck here, any other suggestions?

krobinson
29-07-08, 08:05 PM
I think the wireing to the TPS must be dead. If I unplug it whilst the engine is running, nothing happens. If I plug in a spare one not fitted to the throttle bodie and play with the trigger, nothing happens.

Can anyone else confirm that if they unplug the TPS on their C20LET than nothing happens? lol

krobinson
29-07-08, 08:13 PM
Okay, i've been in and out at the car checking different things.

I'm now 99% sure the wires to the TPS are dead. To confirm this I unplugged the TPS on my cavalier, straight away the rev's rose to 1500rpm and the ECU light came on. When I plugged in my spare TPS sensor, and moved the trigger the rev's moved with it.

So, next thing is, How will I fix this? I'm thinking of just reviring the TPS straight back to the ECU plug. But it's knowing which wires to join it to?!?! Are their any duplicate coloured wires in the loom?

Keith

Ben
29-07-08, 08:47 PM
If this dosent help let me know Keith, will see what others there are,

http://i6.photobucket.com/albums/y228/lurk75/forkeith-1.jpg

krobinson
29-07-08, 09:21 PM
There's 3 wires running to the TPS. One is an Earth however.

What I want to do is connect 2 fresh wires back to the ECU plug, and earth it at the fuel rail. I've stripped back the wires entering the ECU plug, but there's lot's of multiple colours so i've no idea which brown/blue etc it is. I can use the above however to see if the original wires are live or not.

Keith

Ben
29-07-08, 09:34 PM
Keith

Wire1 Brown blue wire goes into the Camshaft position sensor wire which is blue green (wire 3)

Wire3 on the tps is brown green and that goes into the ecu pin 53 as above and the other wire is the earth and it shares the earth on pin 30 see below

http://i6.photobucket.com/albums/y228/lurk75/forkeith-2.jpg

Ben
29-07-08, 09:37 PM
Heres the wiring diag..

http://i6.photobucket.com/albums/y228/lurk75/forkeith-3.jpg

Ben
29-07-08, 09:38 PM
B147 is the TPS and B132 is the camshaft sensor

Ben
29-07-08, 09:54 PM
lol this one might help too...

http://i6.photobucket.com/albums/y228/lurk75/forkeith-4.jpg

Ben
29-07-08, 09:58 PM
repost

Ben
29-07-08, 10:06 PM
Im getting sad now, but just incase you didnt know...

http://i6.photobucket.com/albums/y228/lurk75/forkeith-5.jpg

krobinson
29-07-08, 10:08 PM
Keith

Wire1 Brown blue wire goes into the Camshaft position sensor wire which is blue green (wire 3)

Wire3 on the tps is brown green and that goes into the ecu pin 53 as above and the other wire is the earth and it shares the earth on pin 30 see below



So that would say to me that the wire most likely to be dead is the brown/green, because it doesnt share this wire with any other sensor?

This gets more confusing than I thought... :thumb:

Ben
29-07-08, 10:11 PM
by process of elimination yes it would say that, but do what the troubleshotting says and get a multimeter across the pins in the plug to check it, the wire going to the CPS could be off as iirc you had the loom custom made so could be a dodgy solder or similar,

I think its straight forward but i got the diagrams sat in front of me lol.

Fancy looking at the din data on the 1.0 corsa c and the astra gsi turbo as they share the same ecu but just use different pins lmao

krobinson
29-07-08, 10:13 PM
Could be, will check that tomorrow after the purchase of a multimeter. Thanks Ben!

Ben
29-07-08, 10:14 PM
No probs mate, need anything else i will have a browse but tbh think thats all there can be.