Why Rover 75 ECU goes wrong?

[murphyv310]

Hi.
I have heard many theories regarding ECU failure. EEPROM corruption can be caused by low voltage. The reason this happens in many cases is trying to start your car with a low battery. This causes the nominal voltage to drop to a level that the internal regulators in the ECU do not have enough headroom to give a stabilised 5 volts or 3.3 volts in addition to that noise on the supply (starter solenoid pulsing) will easily corrupt the EEPROM. If on the the first attempt at staring there is a really sluggish response from the starter then DO NOT attempt to try again, either recharge the battery or jump start the car with good quality leads with a known good battery or replace the battery.

With respect to the ECU ensure the connector and its contacts are clean and dry, all earth connections are sound and that the battery is in good condition and the terminals are secure and coated with petroleum jelly.

If you are technical there is no reason why you should not look inside the ECU for dampness, bulged Electrolytic Capacitors and dry soldered joints, ensure that the seals around the ECU are sound, a smear of Petroleum Jelly or vaseline on them won't go amiss, the same goes for the multiplug connector.

[zsomborovics]

Originally Posted by murphyv310

Hi.
I have heard many theories regarding ECU failure. EEPROM corruption can be caused by low voltage. The reason this happens in many cases is trying to start your car with a low battery. This causes the nominal voltage to drop to a level that the internal regulators in the ECU do not have enough headroom to give a stabilised 5 volts or 3.3 volts in addition to that noise on the supply (starter solenoid pulsing) will easily corrupt the EEPROM. If on the the first attempt at staring there is a really sluggish response from the starter then DO NOT attempt to try again, either recharge the battery or jump start the car with good quality leads with a known good battery or replace the battery.

With respect to the ECU ensure the connector and its contacts are clean and dry, all earth connections are sound and that the battery is in good condition and the terminals are secure and coated with petroleum jelly.

If you are technical there is no reason why you should not look inside the ECU for dampness, bulged Electrolytic Capacitors and dry soldered joints, ensure that the seals around the ECU are sound, a smear of Petroleum Jelly or vaseline on them won't go amiss, the same goes for the multiplug connector.

And what do you think, can the generator cause the damage in the EWS or in the ECU at the moment when we stopping the engine?? How can we exclude this opportunity? how can we measure this? If it's the problem why the fuse is unbroken..

And can the comfort computer cause this? Just it happened sometimes that tha windshield wiper started to work just self. We did not find a short circuit.

[marinabrian]

Originally Posted by zsomborovics

And what do you think, can the generator cause the damage in the EWS or in the ECU at the moment when we stopping the engine?? How can we exclude this opportunity? how can we measure this? If it's the problem why the fuse is unbroken..

And can the comfort computer cause this? Just it happened sometimes that tha windshield wiper started to work just self. We did not find a short circuit.

Does your car have the Sat nav fitted?
I ask as water ingress into the boot can cause issues with the K line, causing corruption to the EWS immobiliser.
Brian

[zsomborovics]

There is no Sat Nav in our car...

[David Lawrence]

Originally Posted by zsomborovics

There is no Sat Nav in our car...

Does your starter turn over sluggishly in that cold weather you have there? Last month in Slovakia I noticed how slowly the engines turn over in the mornings, it could relate to one of the points in an earlier post. I presume your climate is similarly cold.

[murphyv310]

Hi.
Anything that can cause spikes on the supply could possibly cause corruption. Remember these ECU's are now 7 years old at least, supply line filtering which the regulators & any LC (choke & Capacitor) takes care of could have a problem so may not be as efficient, capacitors in this area of the circuitary often change value due in the main to the wide variation of temperature in automotive uses. The failure is different to mains operated equipment with SMPS supplies where the capacitor ESR rises. In this type of ECU capacitor value drops, Tantalum capacitors also can fail very suddenly and the surface mount electrolytic caps can leak.

The alternator can produce spikes and more so if it is worn (Slip rings) but relays opening and closing can do the same.
I would "suspect" that if the ECU gets corrupt due to an alternator fault there has to be a problem with supply line filtering, a couple of 0.1uf caps to decouple the supplies at the EEPROM pins often works and this is a modification done by the manufacturer in this type of equipment.
Hope this is of some use.

[zsomborovics]

Hy,

In general what can cause battery full drain during 2 days??? Of course no lamps on and the key is not in the ignition switch.... Or maybe the battery is bad, and this cause corruption in the ecu...

The battery was examined by experts but they could say maybe good, maybe not...

Thanks,
zsomborovics

[Lovel]

Originally Posted by zsomborovics

Hy,

In general what can cause battery full drain during 2 days??? Of course no lamps on and the key is not in the ignition switch.... Or maybe the battery is bad, and this cause corruption in the ecu...

The battery was examined by experts but they could say maybe good, maybe not...

Thanks,
zsomborovics

Sounds like you may need to check for parasitic drain on the battery.

Remove -ve battery lead and with meter between lead and battery post on Millamps scale you should see 0.3 Millamps possibly upto 0.5?. If you see any higher values than this start removing fuses one by one to try and find with fuse circuit is taking the current.

[zsomborovics]

Thank you Lovel!

We checked this and the meter shows 0,3-0,4 amper!! If we remove the control unit (black computer near the fuses we call it comfort computer), and if we remove the fuse of the fuel heater system, the meter shows 0,04-0,02 amper.... The fuel heater system draining 0,1-0,15 amper...

But how can 0,5 amper draining the battery fully during 2 days? 0,5X48 hour is just 24 amper but the battery can 80 ah. Interesting....

[marinabrian]

Another common "culprit" of battery drain on the diesel variants is a faulty glow plug relay.
These are often overlooked post plenum flooding, however if they get wet, they remain wet, and a "glowplug relay incorrect state" is a common failure on our cars.
Brian