Brake Light Woes - Can Anyone Help?

[stevebev]

I'm just a keen DIYer btw, but hoping somebody can shed some light on the weirdness I'm getting... My brake lights don't work and I get very occasional problems when starting the engine (Vectra C 1.8 2002)

On the starting issue - sometimes (but infrequently) when I turn it over it idles roughly/judders and then stalls. Start it again and all's well for the next 10-15 attempts.

The brake lights are even weirder;they work for 1-5 mins until the MIL comes on, at which point they stop working and won't work anymore until I reset fault codes. I've replaced the pedal switch just in case, checked the fuse and all rear lamps/3rd brake light - everything checks out with a meter. (The brake lights seem to work properly and indefinitely if the engine isn't started, and only stop when the engine's started and the MIL comes on, always giving the two codes below):

P0170 (Fuel trim)
P0571 (Brake switch A circuit)

I reset the MIL before I looked at the fuel trim levels, so am not too sure where to start on the P0170. I'm guessing I should check for leaks/clean the MAF?

Any help really appreciated - I've been tearing my hair out over this (and can't afford to lose what precious little I have left

[whiskyno7]

mass air flow/ and egr valve sound like how mine was till i got mine sorted out. but lights ??? cant help sorry

[stevebev]

Crikey! - I thought my post was a bit late in the day but thanks for the pointer

[stevebev]

Update: A clean of the MAF sensor wires cleared the P0170, but brake light still triggering an error (but only with engine running after a variable few minutes). I'm guessing an intermittent short/break caused by engine vibration in the loom somewhere. That'll be fun to find if it is...

[Das]

See if you can find the earth for the lights and give it a good clean. Id even pull the fuses and check theres not a bit of corrosion on them, long shot I know but thats whered id start.

[stevebev]

...anything's worth a go right now - cheers

[stevebev]

After a long day with a wiring diagram (courtesy of a Haynes manual I ordered yesterday from Amazon) and a probe/meter, have finally found the culprit; a loose connector to the passenger side fusebox/control unit (behind the glovebox). Problem sorted (and cruise control working again - it wasn't but raised no fault code other than the brake circuit one).

Relieved to have it sorted - can't imagine what the bill would have been via VX

[Das]

Great result. Always satisfying sorting a problem like that.

[TonyP2020]

Yes, well done.