P0172 & P0175

[mcweasel01]

👀

What a month! Worry free motoring, even decided to treat it to a brand new set of Goodyear's last week.

A day later the weather improved and BAM, like a slap in the face, P0172/P0175 is back

Piece of junk

Anyways, got the mechanic back out today and....

Nothing. He's got nothing at all. Every single test comes back clear. 

No vacuum faults. No compression issues. All cables etc fine. He doesn't know what to suggest next. He's even more stumped that it only occurs when the weather is 'hot' (usually over 21°).

Back to the drawing board

[RL123]

What about all the u (communication codes you posted earlier) ? may be worth checking the BCM/Fusebox for water ingress and slap the dash/cluster when the fault occurs if you haven’t done so already.

 

[mcweasel01]

1 hour ago, RL123 said:

What about all the u (communication codes you posted earlier) ? may be worth checking the BCM/Fusebox for water ingress and slap the dash/cluster when the fault occurs if you haven’t done so already.

 

Excellent point, I'll need to give it a few days for the codes to reappear (cleared today), but one was definitely to do with sunroof closing speed error (it doesn't have a sunroof!)

Engine bay fusebox is completely free of water ingress, I'd need to check the footwell one, I do get a lot of water on the passenger door sill (when it rains we have to open door and wait for the water to clear).

Could it be shorting something when the temperature gets warm though? And would this generate running too rich? 

Only other thing the mechanic noted was that when he turned it on, the temp sensor 1 on the cat was showing 410° despite not being used since Thursday

[RL123]

When the communication is lost between modules, the system assumes data that is missing and can throw up all kinds of false errors.

it is the passenger side footwell fuse box/BCM that suffers from water ingress probably from the windscreen. Usually get a wet footwell carpet as well.

I have read there are some connectors in the A pillar at dash level that can give issues.

my son’s Focus cluster played up when it had been running for some time. Stopped for say 20 mins to let it cool down and continued the journey ok. Didn’t do it cold or on short runs. Whacking the dash brought it out limp home mode for mile or two.

[mcweasel01]

Plugged it in today, P0175 is sat in pending, no sign of P0172 yet.

Also bunch of other codes. Brake light fault is true, I need to get that replaced (again), or just remove/put back in as I only replaced it a few months ago.

Should I pull the fuses for anything & try to reset the ECU etc?

[unofix]

I would start with clearing ALL the DTC's. Then disconnect FORScan. Reconnect FORScan and force it to create a new profile for the vehicle when it asks. Then rescan all modules again. From what I can see many of those codes date back to when Noah built his ark !!

[mcweasel01]

Haha, yeah there are a lot of codes, and they do get cleared regularly, but clear then create a new profile & give it a few days

Probably worth deleting the existing profile once I've cleared?

[mcweasel01]

13 hours ago, unofix said:

I would start with clearing ALL the DTC's. Then disconnect FORScan. Reconnect FORScan and force it to create a new profile for the vehicle when it asks. Then rescan all modules again. From what I can see many of those codes date back to when Noah built his ark !!

Done that, interestingly though, P0175 was no longer showing in Pending before I cleared it!

But anyways, reset DTCs, created a new profile (it asked for CMax or Focus, went CMax) and immediately DTCs were present! I've cleared them off, and will give it a few days to see what else crops up.

Would it be worth running Forscan as a Focus? See if anything crops up there?

[unofix]

"U" codes are communication errors on the canbus. The most common problem on a 2011 C-Max would be poor solder joints on the instrument cluster. The second most common problem would be water ingress to the GEM unit.

[RL123]

The first time I’ve noticed a lin bus dtc on printouts. This is the link between the module and sensor/component I believe.

it this case it appears to be the RH windscreen wiper. 
could this be pointing towards BCM rather than cluster?

[mcweasel01]

Heeey! Happy Sunday. Maybe. Hopefully.

So I've given a few days after clearing the previous DTCs, created new profile etc cleared those codes, then deleted both profiles, and created a new one completely.

Plugged in today as weather better, and it struggled a bit yesterday. 

No 0172/P0175 (wooooooo) but these are now showing. Checked both fuse boxes, no sign of water ingress & passenger footwell dry.

Pics attached, seems common for short circuit. Poor solders likely? How easy would that be to fix? Remove & send off?

I ran the live data from cold, hadn't been driven for around 24 hours, so temps etc are what it's showing from cold (if that makes any difference)

Thanks for all the help you've all provided so far! Hopefully we're getting into the final stretch. Or I px it for a Mazda.