Lucas 14 CUX ECU - Is it adaptive?
Discussion
Hi All
Does anyone know if these ECU's adapt to driving styles, or go into a limp mode that needs resetting after a component failure?
I've recently taken over a 1989 3.5 Range Rover Classic that had been driven very slowly for a long time (my 90 year old dad!). It had a TPS failure - no ou put signal, that I've corrected. Now, the concern is the ECU is only putting out 4.3 volts to the TPS. I've got a spare ECU and this does exactly the same. The RR workshop manual mentions min voltage of 4.6v. The effect of this is that instead of the TPS putting out 4.6 v at full throttle (as per the manual) its only putting out 3.7v.
Does the ECU need time to adapt to the new TPS?
Thanks for any help in advance.
Does anyone know if these ECU's adapt to driving styles, or go into a limp mode that needs resetting after a component failure?
I've recently taken over a 1989 3.5 Range Rover Classic that had been driven very slowly for a long time (my 90 year old dad!). It had a TPS failure - no ou put signal, that I've corrected. Now, the concern is the ECU is only putting out 4.3 volts to the TPS. I've got a spare ECU and this does exactly the same. The RR workshop manual mentions min voltage of 4.6v. The effect of this is that instead of the TPS putting out 4.6 v at full throttle (as per the manual) its only putting out 3.7v.
Does the ECU need time to adapt to the new TPS?
Thanks for any help in advance.
It does have adaptive capabilities and also does have a 'limp' mode, but neither of these would account for the TPS voltage being wrong. Are you sure you have the pin-out correct? If the ECU goes into limp mode, it should also register fault codes to explain why. Limp mode (and any associated fault codes) would be reset if the battery is disconnected or the ECU is unplugged for ten seconds.
ETA I recall that the ECU is very fussy about getting the correct TPS voltage at idle and this needs to be calibrated carefully by adjusting the position of the pot.
ETA I recall that the ECU is very fussy about getting the correct TPS voltage at idle and this needs to be calibrated carefully by adjusting the position of the pot.
Edited by GreenV8S on Wednesday 1st August 18:01
I haven't reset the ECU. Is this a case of unplugging it from the car for a few minutes?
The TPS volt output and resistance on idle is within range. What the RR manual doesn't say is what the TPS resistance should be on full throttle. So I can only determine whats happening by the voltage.
Perhaps the ECU will adapt to the new TPS and a slightly more spirited driving style after its been used for a few miles?
The TPS volt output and resistance on idle is within range. What the RR manual doesn't say is what the TPS resistance should be on full throttle. So I can only determine whats happening by the voltage.
Perhaps the ECU will adapt to the new TPS and a slightly more spirited driving style after its been used for a few miles?
Contact this PH member as he knows the system inside out, he often solves problems for TVR V8 owners with the same system, he posts to the TVR Forum https://www.pistonheads.com/gassing/profile.asp?h=...
You might want to work through this section of his website:
http://www.g33.co.uk/pages/technical-fuel-injectio...
ETA You'll note in it & in the ACT site that he also links to that they speak of elongating the screwholes in the throttle pot so it can be adjusted - as was the case with the previous ECUs.
http://www.actproducts.co.uk/2011/lucas-14cux-fuel...
http://www.g33.co.uk/pages/technical-fuel-injectio...
ETA You'll note in it & in the ACT site that he also links to that they speak of elongating the screwholes in the throttle pot so it can be adjusted - as was the case with the previous ECUs.
http://www.actproducts.co.uk/2011/lucas-14cux-fuel...
Edited by paintman on Wednesday 1st August 21:45
As the sensor readings are ratiometric a low voltage reference value for the TPS should not actually cause any issue!
(ie, the nominal 5v reference that is sent to the TPS is also used as the reference for the Analogue to Digital Converter (ADC) so ratiometry is maintained pretty much no matter what the reference voltage ageing actually is
(ie, the nominal 5v reference that is sent to the TPS is also used as the reference for the Analogue to Digital Converter (ADC) so ratiometry is maintained pretty much no matter what the reference voltage ageing actually is
Freddie328 said:
I haven't reset the ECU. Is this a case of unplugging it from the car for a few minutes?
It will reset after being disconnected for ten seconds.If you aren't getting 5V across the TPS there is something fundamentally wrong and you need to get to the bottom of that.
With the ECU disconnected, you should read 5kOhms between pins 5 and 25 of the ECU connector. Pin 20 should be connected to the TPS wiper and you should see the resistance between the wiper and ground vary smoothly as you move the throttle. The ECU senses the voltage at the wiper. You should see 0.26-0.36V at idle and at least 4.6V at full throttle. But of course you won't get 4.6V if the supply to the TPS is less than that. In this case I suggest you check for a voltage difference between ECU ground and vehicle ground. You can measure the voltage at the ECU connector by inserting a fine wire into the connector housing - this should confirm the voltage at both ends of the loom are the same.
Hi,thanks for your reply.
Im getting 5k ohms between the wiper and ground, with a smooth progression as the throttle is opened.
The low TPS input voltage is measured whether I test through the ground wire to ECU or through car chassis.
Do you think there may be a connector between the ECU and TPS that has high resistance? There's no obvious connector blocks.
Im getting 5k ohms between the wiper and ground, with a smooth progression as the throttle is opened.
The low TPS input voltage is measured whether I test through the ground wire to ECU or through car chassis.
Do you think there may be a connector between the ECU and TPS that has high resistance? There's no obvious connector blocks.
Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff