Tune Resistor - ECU Mate "Limp No CATS"

[MPoxon]

Evening all,

The Griff seems a bit less responsive than it used to be and I am now hitting the rev limiter at about 5.5k instead of 6.25k. I plugged my Steve Heath ECU mate in and the map selection is showing as "Limp No CATS". According to the manual this means that no Tune resistor has been detected and the map selected is the Limp Map.



My car has a Tornado ECU fitted. I have spoken with Mark Adams and he says that the ECU must either be fitted with a white tune resistor (CAT) or a green tune resistor (NON CAT)

At the local PH meet I plugged the reader into two other TVRs with 14CUX and they both also read "Limp NO CATS". One had a TVR Power EPROM, the other standard.

Does anyone else have a 14CUX with a tune resistor fitted and an ECU mate? What does yours show?

Thanks in advance

Matthew

[shpub]

Try starting the engine and then see what comes up.

[brittanytvr]

Hello,
I have bought also an Ecumate and found that my Chim has a "green resistor no cats" and saw the resistor near the battery !!
A guy who knows Range and land V8 told me that I can disconnect the Lambdas if I have a green resistor, I have tried this and the message is the same on the ecumate " Limp no cats" but the car is running correctly, perhaps your Lambdas are not connected??
Chris

[blitzracing]

Dont forget limp means the ECU is in fall back mode- so check for error codes. After you have done this, then try an ECU unplug and replug to reset the ECU, then start the engine and see if the map goes back to white tune (assuming you have cats). The Limp home map is not resistor dependent, but is normally caused by another sensor being out of range for a period. The ECU mate is quite happy to show the correct map- Adams chip or otherwise, its not a TVR thing.

Edited by blitzracing on Sunday 19th August 08:44

[EGB]

Matthew. We both have 1999, 500s and presumably with white resistors. Where are these found, and look like, on our Griffs.
Can they sometimes be defective to confuse the ECUmate? or will the ECUmate tell us if they are defective? Steve will help on this. Thanks, Eddie

Nice pic.

Edited by EGB on Sunday 19th August 10:55

[Loubaruch]

The Ecumate readout with my completely standard 500 is fine, everything displaying as it should. The performance is also well in excess of my capabilities so will leave everthing standard.
I have noticed on here that those with modified engine management seem to have an inordinate number of problems, perhaps there is a message there!

[MPoxon]

This is what the tune resistor looks like Eddie:



There is a small blue connector in the loom near where the relays are where this connects in.

I will try all the suggestions above later today and report back.

[blitzracing]

Sorry to repeat myself- BUT the limp home map is NOT resistor dependent- its either got a fault code logged, or its simply displaying the wrong map on power up, and you simply need to start the engine to get the correct map.

[shpub]

blitzracing said:

Sorry to repeat myself- BUT the limp home map is NOT resistor dependent- its either got a fault code logged, or its simply displaying the wrong map on power up, and you simply need to start the engine to get the correct map.

It doesn't measure the resistance directly.

ECUmate looks at the internal pointers etc and works out which map the ECU is using. It then describes the tune state based on the map selection.

As Mark says, the limp home map selection is the ECU default. The ECU will select one of the other maps based on the tune resistance it measures but it will default to the limp home map if there is a problem.

[EGB]

Thanks Matthew, Mark, Steve............Luke and John. Useful thead this.

[MPoxon]

Afternoon gents, thank you all very much for your replies.

I powered the car on today and the ECU Mate still reads "Limp No CATS"

It looks like the ECU is not detecting any resistance and putting the ECU into the default limp map.

After a 10 minutes of fiddling with the loom and re-making the connections on the tune resistor - powered on and now get the correct reading "White + CATS"


Steve good to see you still lurking around the TVR forums, thanks for your help I know you must be very busy with the Phd.

Eddie if you are after useful information then have a ganders through this - very useful indeed:
http://www.actproducts.co.uk/category/lucas-inject...

My next question is if you have a car with o2 sensors but it does not have any cats should you run a white tune resistor or a green one? My understanding is that the white tune uses o2 sensors where as the green tune ignores them.

[blitzracing]

If the resistor is open circuit or disconnected it defaults to map 5, it wont force it into the limp home map, so you still have (or had) another issue. Did you check the error codes? The green map ignores the lambda probes, but unless you have a specific map for your engine (not the default TVR chip) its not recommended. You need the white one for the catalysts.

[MPoxon]

blitzracing said:

If the resistor is open circuit or disconnected it defaults to map 5, it wont force it into the limp home map, so you still have (or had) another issue. Did you check the error codes? The green map ignores the lambda probes, but unless you have a specific map for your engine (not the default TVR chip) its not recommended. You need the white one for the catalysts.

Hi Mark,

I have checked the ECU for any fault codes and none are present. All of the readings shown by ECU Mate seem to be (from my very limited experience) OK.

The tune resistor is an interesting one as e according to a number of sources Map 5 (open circuit) is described as a limited limp map. But this is different to Limp mode which can occur on any map if the ECU detects an issue.

Colour	Value	Catalyst	Application
Red	180Ω	No	Australian 3.9
Green	470Ω	No	Europe & UK 3.9 (or 3.5 Disco)
Yellow	910Ω	No	Gulf States 3.9, or Europe & UK 4.2
Blue	1.8kΩ	Yes	Gulf States 3.9, or Europe & UK 4.2
White	3.9kΩ	Yes	Europe & UK 3.9 (or 3.5 Disco)
N/A	Open Circuit	Yes	Limp home map

I don't know enough about the subject but it would appear that where mine was running on map 5 it was not mapped fully as I was hitting the rev limiter early and the car did not feel overly responsive. The ECU mate was not showing any error codes and I believe in the throttle screen it will show "LIMP HOME DETECTED" on the screen if the ECU has detected an error.

I think I will leave mine with the White Tune resistor in for the time being until such a time as I can get the car to Mark Adams to work his magic on the car.

Matthew

[blitzracing]

Umm.... There are wiring looms out there with no resistor fitted for the North American market, and these go to map 5, and as the 3.7 k ohm resistor is the highest value of tune resistor, its always appeared to stick to "a" catalyst tune (seen by the mixture cycling) with the resistor removed or open circuit -Ive always assumed its the same map ..... but I had some dealing over the last few days with a Russian chap who was trying to change maps, and whatever he did with resistors it stuck to map 5- so we have a situation where the Eprom is programmed to stick to map 5, with or without resistor, so its appears not to be reliable to assume that open circuit is Cat tune map 5, backed up by your observations. Ive also just checked the Ginetta without a tune resistor and it sticks to limp home, so all I need now is a cloth to wipe that egg of my face.

[FlipFlopGriff]

The tune resistor is usually tucked up behind the small flappy bit of carpet in the passenger footfell below the glove box on the right hand side. Probably well glued down so you'll need to remove it first.
Our 500 ran better with a non cat tune resistor why???
FFG

[blitzracing]

FlipFlopGriff said:

The tune resistor is usually tucked up behind the small flappy bit of carpet in the passenger footfell below the glove box on the right hand side. Probably well glued down so you'll need to remove it first.
Our 500 ran better with a non cat tune resistor why???
FFG

It removes the lambda cycling completely and no longer tries to keep the mixture at lambda 1, so you can run richer at low speed that reduces the shunting, and leaner at cruise that gives a better MPG. The peak power does not change. Only if you have the correct non cat map however-

[MPoxon]

blitzracing said:

It removes the lambda cycling completely and no longer tries to keep the mixture at lambda 1, so you can run richer at low speed that reduces the shunting, and leaner at cruise that gives a better MPG. The peak power does not change. Only if you have the correct non cat map however-

I might give the green one a go in that case. Mine does not have any cats and has a Tornado EPROM which is mapped on both white and green maps.



That is interesting about your Russian customer, I wonder what EPROM he has if the tune resistor is not making any difference to the map. I assume he has tried measuring the resistance between pins 5 and 27 on the ECU plug to make sure the resisor and loom connections are reaching the ECU OK?

[shpub]

The NA version had the map preprogrammed in the ECU to use a specific map usually 5. Many of the NA Land Rovers/ecus ended up outside NA though. This meant that they had no tune resistor facility.

Some ECUs also had other functions preprogrammed out such as the gearbox selection.

The ECU has several levels of limp home. If a sensor fails, the ECU will often use a limp home value with the current map. Tpot for example.

Ecumate will actually indicate this in its throttle display/test window.
In more serious cases or if it can't detect a tune resistor when it expects one, it goes to the limp home map.

[blitzracing]

MPoxon said:

I might give the green one a go in that case. Mine does not have any cats and has a Tornado EPROM which is mapped on both white and green maps.



That is interesting about your Russian customer, I wonder what EPROM he has if the tune resistor is not making any difference to the map. I assume he has tried measuring the resistance between pins 5 and 27 on the ECU plug to make sure the resisor and loom connections are reaching the ECU OK?

Only if you dont have catalysts in place, or you might cook them with the wider mixture changes. And yes he did measure the pins. :-)

[Richieboy3008]

No cats you say? Scare the dog away and they'll come back!