MIL light after airbox off job

[sweeper]

Recently the engine was starting badly and the engine running rather lumpy. Finally checked the starter battery and voilá, it was definitely at the end of its lifecycle.

I replaced with an Optima Red Top, which was an airbox-off due to the size of the previous battery. At the same time I replaced the big fuse and properly greased all terminals. Right after the change, the car ran as new, with the engine starting without hesitation, great acceleration and smooth engine... for a couple of days.

Now the MIL comes on sporadically: First only once for 1/2 second, then a couple of times when cold during acceleration, now regularly. Clearly not being a technician I assume the folowing:

- Airbox not sealed properly
- One of the sensors not fitted correctly
- Interferences between engine loom and HT leads (at least I read something here about spikes?)
- ...

Any suggestions gents?

[Gazzab]

You need a laptop to check ecu.
Probably nothing to do with battery change. Probably the air temp sensor on its way.

[Mr Cerbera]

Possibly the Air Temp sensor on the passenger side of the air box not connected properly ??

[sweeper]

Just ordered a new air temp sensor. Luckily one of the cheaper parts, so I will give this a try as connectors all sitting tight.

Never managed to get connected to the ECU unfortunately, but thats another story :-(

[sweeper]

Had a look at the sensor today and found it half way covered in glue! Tried to clean it off but will replace it anyway.

Is there anything for the ECU to re-learn if I change the sensor?

[Tanguero]

If you want to know what is causing the MIL light instead of guessing and replacing stuff at random you need to get the diagnostic software working...

[Mr Cerbera]

Ooooh, so glad that you mentioned that....

Anyone know if you can connect the ECU to a modern Laptop equipped only with USBs ??

[gruffalo]

You need to buy an adapter.

[Tanguero]

Use a USB to serial adapter and set it to appear as COM1. You may need to run the ECU software under XP compatibility mode in windoze 7, but not having used that myself I don't know.

The key is getting the virtual serial port from the adapter to appear as COM1 as the software is hard coded to use this by default.

[sweeper]

I should have expected this...

When I tried to connect to the ecu a couple of months ago I went through every related post on PH and sat for hours next to the passengers footwell. I decided to give it a break as I was close to throwing the laptop out of the garage.

Anyway, you are right of course and I think the time has come for the ecu connection test pt.II - however I might have to open a new thread to fire my questions at you

[noddy2]

Back to Topic,
MIL Light will not be triggered by Air Temp sensor being badly connected or not connected at all.
You need diagnostic software for the car,most likely areas of fault are,Lambda Sensors,Throttles, Wiring Loom fault or moisture ingress into the wiring connectors.
Hope this helps.

[sweeper]

Thanks noddy. Not at the car for a while now but will check this when I am back home.

[tejr]

noddy2 said:

Back to Topic,
MIL Light will not be triggered by Air Temp sensor being badly connected or not connected at all.

Yes it will.. if we are talking about the sensor plugged into the nearside airbox/intake pipe.. Unplug it and the MIL will come on..

It gave me a scare when I left it unplugged once..