Td5 disco manual limp mode

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Andy345

New Member
Posts
43
Location
Rustington, West Sussex
Hi guys, I've got problem with the old disco going into limp mode.

The car will start fine and idle fine and will almost always rev up to 2000 in neutral.

I can pull off the drive and start to drive down the road but within 5 meters the car will go into limp mode. Ignition off and on again will give back use of the throttle but again the car will go into limp mode before I can get back to the driveway.

I have recently changed the rocker cover gasket and loom and also cleaned all traces of oil in and around the ecu and loom including the red plug.

I have put a second hand pedal/ potentiometer on to no avail. I can borrow another pedal off another td5 to test if needs be.

Managed to borrow a one month old Bosch s3008 battery as I was looking down the knackered battery route.

I've read of a permanent 5v feed going to the throttle pot and if the 5v drops it will knock out the throttle pot but I'm not sure how to check this.

I've had a search through a few posts and although I can find little bits relating to my issue not anything which completely relates.

Any thoughts or ideas guys please?
 
Andy345 said:
Hi guys, I've got problem with the old disco going into limp mode.

The car will start fine and idle fine and will almost always rev up to 2000 in neutral.

I can pull off the drive and start to drive down the road but within 5 meters the car will go into limp mode. Ignition off and on again will give back use of the throttle but again the car will go into limp mode before I can get back to the driveway.

I have recently changed the rocker cover gasket and loom and also cleaned all traces of oil in and around the ecu and loom including the red plug.

I have put a second hand pedal/ potentiometer on to no avail. I can borrow another pedal off another td5 to test if needs be.

Managed to borrow a one month old Bosch s3008 battery as I was looking down the knackered battery route.

I've read of a permanent 5v feed going to the throttle pot and if the 5v drops it will knock out the throttle pot but I'm not sure how to check this.

I've had a search through a few posts and although I can find little bits relating to my issue not anything which completely relates.

Any thoughts or ideas guys please?
Click to expand...

How do you know it's going into "Limp Home" mode? If yours was an auto it would be very clear, but on a manual it's not so straightforward to identify.


Dave
 
Andy345 said:
Ah sorry I've got the engine light one and complete loss of the throttle pedal
Click to expand...

Well I wouldn't call that "Limp Home" mode at all and I think you will confuse others if you call it that.

You may have a throttle pedal problem but to be sure it needs checking with a diagnostic terminal should as Hawkeye or Nanocom.

Re the 5v comment; the throttle potentiometer has 2 or 3 tracks (depending on age and engine type 10P or 15P) the 2 tracks have contre readings which add up to 5v.

For example at tickover the readings might well be: track 1-1v and track 2 - 4v, adding up to a total of 5v.

At medium throttle track 1 - 2.5v with track 2 - 2.5v. Giving a total of 5v

At full throttle track 1 - 4.5v with track 2 - 0.5v. Ditto.


Get the track voltages read before doing anything else, that's my advice. Also check for general engine fault codes.

Dave
 
Hi Dave thank you for your help.

Can I get a quick run down on limp mode?

We had nanocom on it the other day track one and two we're behaving as they should be up until the loss of throttle at which point we would loose track 3.

I need to go and get the nanocom back on Wednesday and plug it in again as we did have a driver demand error but can't remember the code atm.

We will chuck the other peddle on at the same time just to narrow down.

Thank you
 
Andy345 said:
Hi Dave thank you for your help.

Can I get a quick run down on limp mode?

We had nanocom on it the other day track one and two we're behaving as they should be up until the loss of throttle at which point we would loose track 3.

I need to go and get the nanocom back on Wednesday and plug it in again as we did have a driver demand error but can't remember the code atm.

We will chuck the other peddle on at the same time just to narrow down.

Thank you
Click to expand...

Limp Home mode is a term used in the modern car industry to indicate that the main ECU controlling the engine has detected a potential problem and as a result de-tunes the engine, thereby reducing the possibility of further damage. It also affects the automatic gearbox by mandating a 3rd gear-only operation.

Once the Nanocom is connected, select the demand pedal operation and you will be able to see the changing voltages as you press the pedal. Look for any drop-outs throughout it's travel.
 
Last edited:
+1 for everything Dave said, there's no such thing as "limp mode" for a manual, it's only for auto, on a manual there are faults which can affect engine behaviour that's all...what year is the D2 by the way

the MIL + driver demand fault means the problem is deffinitely on the TP sensor circuit but if the pedal is ruled out there still remains the wiring issue which must be checked and that's not easy cos the inputs from TP to ECU are hardwired but going through the engine bay and the wiring might be chaffed somewhere, if the problem is with the supply to the sensor then a header is involved where bad contact can be

check T1 and T2 inputs on live data, T3 would not trigger the MIL nor noticeably affect engine running
 
Thank you fery, I've had a second pedal on it (used jobby off eBay) I'll chuck the third definitely working one on, on Wednesday just to completely rule out the pedal.

Feed wire from the ecu am I right I thinking this feeds a numbers of items or is just the one for the pedal and another for other bits?
 
the ECM has different power outputs for each managed circuit, for TP it's only one from pin 14 of black plug... a contact spray in that plug won't hurt
 
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