172 cup cranks for 3 seconds, wouldn't start, red immo light staying on

[the_jons]

I had a problem on my '03 plate 172 cup, where I would key on, the engine would crank for about 3 seconds then stop - and the red immobiliser light stayed permanently illuminated. If I turned the key to pos 2 & left it for a few seconds, then try to crank I'd get no cranking at all...
Read several threads on here suggesting various issues
http://www.cliosport.net/forum/show...r-on-a-ph2-172&highlight=172+cranks+but+stops
http://www.cliosport.net/forum/showthread.php?596427-Car-turns-over-but-won-t-start/page2&highlight=172+won't+start
http://www.cliosport.net/forum/showthread.php?611496-Urgent-help-needed.-172-cup-won-t-start-(&highlight=172+won't+start
http://www.cliosport.net/forum/showthread.php?580136-Starting-Fault.&highlight=172+fuel+pump+prime
http://www.cliosport.net/forum/showthread.php?428427-Car-won-t-start
I stuck my OBD scan tool on it as some threads suggested, could get live data & no DTC's, so I guess all crank / TDC / cam sensors are ok, and guess as well that the purple & white CAN twisted pair between the ECU & UCH (what does UCH stand for by the way?) is OK.
I checked the fuses & relays for continuity, Fuses were OK, but I struggled to get a good test on the relays (had to jiggle the DVM probes on the relay spades to get continuity on the solenoid side) ...so...
20 minutes of sanding the spades & a bit of a squirt of WD40 on the contacts and it fired up straight away!
Thanks for all suggestions in the posts listed above that helped me quickly (& cheaply!) fix my car!

Jonno

 

[lewisredfern001]

Great news m8. Mine has been sat since before Christmas with this problem. I'm really struggling with gettin time to do more work on mine. My beemers just thrown a load of sensor faults, alternators gone AWOL and due a service so having to concentrate on that for now.

My relays where a little crappy and I've cleaned most of them. Maybe I shall give em a few hours of dedicated cleaning time over the weekend!!

Cheers

 

[VenomUK]

What was the outcome. I’m not sure what replays I need to clean if someone could post some pictures please?

The car has been starting fine but took it to get the tracking done and now I get 3 cranks and cuts out. If I leave in pos 2 I get nothing. But have noticed the immobiliser light just keeps flashing. All the same symptoms as the original post.

So assuming it’s fuse issues? But where do I begin please?

 

[GrahamS]

Flashing is the chip not being recognised, usually a key fault. Solid light is typically the gearbox earth or the three smaller relays in the engine bag fusebox, the one which controls the immobiliser will have failed. Swap them round as first port of call.

 

[VenomUK]

I sorted it in the end. I popped the large yellow relay out and that was clean but gave it a rub down regardless and a bit of DW40

I also pulled the blue 5 amp fuse out which was looked pretty bad, so gave that a very good clean up on the contacts and some WD40 and the car fired right away