Discovery Td5 Auto possible wiring fault

sabredylan · May 22, 2012

Having issues with disco at minute and could do with some help.

New engine and engine wiring loom, Egr removed. Idle a bit lumpy and dips as if I've got a bad earth. Earths checked and appear ok.

Nanocom showing Egr short circuit, Egr stuck closed, Air flow circuit current, Temp sensor circuit current. 1884 falt flag shown in gearbox ecu. No other faults shown in other ecu's

The temp sensor is new but kept maf as readings seemed ok.

Symptoms are down on power, doesn't pull like it should. Revs hanging on gearchange (autobox) sounds like a misfire, takes ages to reach temp and SLS intermitent working.

Found two blown fuses, brake lights (difflock warning flashing when pressing brake pedal) and coolant fan fuse 40 amp. Replaced and made no difference.

Tried unplugging maf made no difference, but coolant temp gauge dropped to cool and red warning light came on.

Thanks in advance

sierrafery · May 24, 2012

sabredylan said:
Having issues with disco at minute and could do with some help.

New engine and engine wiring loom, Egr removed. Idle a bit lumpy and dips as if I've got a bad earth. Earths checked and appear ok.

Nanocom showing Egr short circuit, Egr stuck closed, Air flow circuit current, Temp sensor circuit current. 1884 falt flag shown in gearbox ecu. No other faults shown in other ecu's

The temp sensor is new but kept maf as readings seemed ok.

Symptoms are down on power, doesn't pull like it should. Revs hanging on gearchange (autobox) sounds like a misfire, takes ages to reach temp and SLS intermitent working.

Found two blown fuses, brake lights (difflock warning flashing when pressing brake pedal) and coolant fan fuse 40 amp. Replaced and made no difference.

Tried unplugging maf made no difference, but coolant temp gauge dropped to cool and red warning light came on.

Thanks in advance

just saw this....
1. check the ECT(engine coolant temp.) sensor's wiring if u are certain that the sensor is good. Unplug the ECU red plug and check between pins of the sensor connector...it must be open circuit... then bridge the pins in it and measure between pins 7 and 18 of red plug ... there must be closed circuit this way if the wiring is good... this sensor/it's wiring could cause you trouble:

The ECT sensor can fail the following ways or supply incorrect signal:
l Sensor open circuit.
l Short circuit to vehicle supply.
l Short circuit to earth.
l Incorrect mechanical fitting.
l Signal fixed above 40 °C (104 °F) not detected.
l Signal fixed below 40 °C (104 °F) not detected.
In the event of an ECT sensor signal failure any of the following symptoms may be observed:
l Difficult cold start.
l Difficult hot start.
lDriveability concerns.
lInstrument pack temperature warning illuminated.
l Temperature gauge reads excessively hot.
l Temperature gauge reads excessively cold.
In the event of component failure the ECM calculates coolant temperature from the fuel temperature sensor signal. If this occurs, the limit engine operation if coolant temperature is too high becomes inoperative.
The MIL will not illuminate in an ECT sensor failure.

2. No MIL or M&S lights on? cos here are the 1884 codes(the on/off columns from the right of the table are MIL left, M & S right )
__________________

sabredylan · May 25, 2012

Thanks for taking the time to reply.

The Engine harness to all sensors and red plug is brand new, so I'm happy this isn't the problem. The temp gauge dropping to cold and warning light coming on is happening quite regular now. The gauge will be fine and stay in middle, but then drop and light will come on. When this happens the engine seems to run better and smoother. Cycle the ignition and the gauge comes back up to middle, before dropping again.

I've ordered a new genuine temp sensor at £20. The one I have on at the minute cost £4. I'm thinking plays up as temp rises. I'll see what happens when i replace it.

sandu · Mar 17, 2020

hello,
I am confused about nanocom readings for engine temperature..
the Engine ECU is showing coolant temperature 92 whilst Auto Gearbox ECU is showing 57.
Can somebody tell me if this is wrong and where to look for a solution?

sierrafery · Mar 17, 2020

Compare battery voltage and engine speed inputs as well between the two ECUs and if those are different too check the ECM red plug to not be oil in it cos that can mix up the CAN messages, i can't check on mine to rule out a glitch cos mine is manual ... also give it a reset to the addaptive values i ''utility'' if you didnt untill now

sandu · Mar 17, 2020

voltage are similar in all ECUs...
I did already the reset of adaptive values...
ECM red plug - I thought about this already and cleaned the plug. Can't say there was too much oil...
No difference after this though.

sierrafery · Mar 17, 2020

sandu said:
voltage are similar in all ECUs...

I just realised that the voltage is not sent via CAN. The RPM is more important cos if it's similar means that the CAN-bus wiring should be OK then it can be a reading glitch or the EAT ECU has a problem, would be good to rule it out eventually if you have a friend with similar vehicle read the engine temp on that too just to make sure it's not some nanocom trick cos the ECT readings should be the same in both ECUs

Discovery Td5 Auto possible wiring fault

sabredylan

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sierrafery

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