tune resistor out of range

[andy-w]

i have just connected an ecu fault code reader to my chim and got the fault code 21...tune resistor out of range...has anyone got any idea where this is and how i can check it???

[david beer]

Had just the same, passengers pressing hard on the footboard had cracked the resistor. Its on the ecu loom, has two wires and will have a clear cover protecting it and will also have a LRover part number. 470 ohm for for non cat,3900 for cat.

[andy-w]

cheers david...its your ecu reader i am using!!!

how big is it roughly...i shall go and have a look at it now, do you know if there is any way of testing it?

[parrot of doom]

Thats the one I think, a new one will be a few pence only.

[andy-w]

Cheers pod. Would any resistor do, so long as it is the same ohms? If not, any ideas where I can get one?

[parrot of doom]

It needs to be the same value, the same tolerance, and have the same temperature rating.

Just snip it out, take it to Maplin etc, and get an identical one. I bet it costs about 1 pence tops.

If the coloured bands are burnt out on yours, let me know and I'll read the value from mine so you can get a new one.

[andy-w]

do you know what the tune resistor does???

I dont think my car has got the cat on it and i know there are two different values of resistor...with cat and without cat...so i was going to get both, run the car and see which on gets rid of the error.

[GreenV8S]

You don't need to measure it, Dave Beer has already told you what value it should be:

470 ohm for for non cat,3900 for cat

If you have lambda sensors and/or a cat, you should use the cat value.

If you have neither lambda sensors nor cat, you should use the non-cat value.

If you aren't sure what you have and don't know how to find out then this probably isn't the sort of thing you should be fiddling with.

[andy-w]

it has the lambda sensors... the manifolds go into the large y peice where a colleague who has a v8s said thats where the cat would be....whereas the lad i brought the car off said they were straight through pipes and there was no cat...

[andy-w]

hopefully daivid beer will read this!!!

i changed the tune resistor for a 470 ohms one and it ran like a complete pig...put a new 3900 ohms in and it ran really well...trouble is i still have the tune sensor error reading when i connect the ECU reader!!!

By the way i disconnected the vaccum hose and it does not seem to have made any difference...!!!

[HarryW]

Does the ECU fault log self clear or do you need to reset it (disconnected it/battery for 10 secs or so) .

Harry

[s4s280]

At the risk of duplicating some content I just did on the TVRCC forum, I too did the vac line disconnect, not change, even having reset the ECU and run for a good few miles.

Have not changed any resistor yet, but did want to just to see short term what difference it made.

Back to andys post ...

With the green resistor it ran like a pig, changing to the white it was better.

Did you at anytime reset the ECU on change of resistor ?

You say it runs better with the white resistor, what is the reading of the old white resistor.

David stated the ohms readings, but also, David, what was the reading on the damaged resistor ?

Just trying to work out the "threshold" of the resistors on the ECU, the Range Rover resistors on Rimmer Bros are

Red - (1) - PRC8005
Yellow - (1) - PRC8007
White - (1) - PRC8009
Green - (1) - PRC8172
Blue - (1) - AMR2016

David also, theres quite a jump in 470 to 3900 ohms if there are two maps in the ECU, can an adhoc dodgy tune resistor flick in and out the two maps if they are populated ?

[andy-w]

Every time i changed something i disconnected the ecu for 30 seconds...

Must admit with the 470 ohms fuse in i only did about two miles as it was running that bad...maybe i should have given it longer.

as soon as i put the 3900 fuse in it ran a lot better

[IPAddis]

If you use the green resistor, you MUST disconnect the lambdas at the connection 6-12 inches from the lambda sensors themselves. Otherwise it WILL run like a very confused pig!

I wouldn't assume that yours is a non-cat though. Sounds like something someone would say to increase the purchase price but it's relatively expensive to get a non-cat pipe and you are likely to have MOT problems.

Ian A.

[andy-w]

is there any difference between the Y section of exhaust between cat and non-cat?

I think i shall give it a go without the lambda sensors and the green fuse...

[David H]

The pre cat cars did not have such a big pipe just where the two pipes join. This is the area where the main cat sits.

If the car has been completely decatted then the main cat box will have a weld line around it where it has been hacked open, and re welded. The standard weld will be quite neat and you can always tell the difference between them.