Sunday, November 28, 2010 - 02:59 pm, by: Malcolm Hall(Neddy)
I have a new problem with my V8: the catalytic converter overheat warning light came on during a short run. Left it to cool overnight, next day the light came on with the ignition and stayed on when the engine was started. Can't be an overheating cat at that stage so I looked further - people have reported that this can mean a dodgy alternator. No sign of leakage from power steering pump. Battery in good condition and fully charged, 14.6V measured at battery terminals with engine ticking over. Tried clearing the memory (removed fuses and replaced) then jumping Te1 and E1 in the diagnostics port to check for error codes - EFI and ECT reported "OK". Just in case I took the battery terminals off, cleaned them and refitted good and tight - no difference. I guess the next step is to get the alternator output checked properly but does anybody have any ideas for what else to check?
Incidentally I am still waiting for the fault that stops my fuel pump to re-appear (when the "+B" signal goes missing) so no further in nailing that problem so far.
Sunday, November 28, 2010 - 04:26 pm, by: Tom Richards(Tomr)
hi malcolm, the same car i had the +B problem, also had the above problem as you describe. I tried everything, disconnected the sensors etc but couldnt fix it. In the end i removed the dash and put a piece of black elect tape over the symbol as the cat light on appears to be the only symptom
Monday, November 29, 2010 - 12:36 pm, by: Malcolm Hall(Neddy)
Hi Tom - I wonder if this is just coincidence? The M-Rel signal that energises the main EFI relay comes from the ECM and although I haven't been able to check it on mine yet, it's likely that this signal being missing or low is what causes my +B signal to go astray. It's the ECM that processes signals from the overheat sensors and drives the warning light. Did you check your ECM for poor contacts or dodgy earths by any chance?
Monday, November 29, 2010 - 01:20 pm, by: Tom Richards(Tomr)
hi malcolm, I tracked it back to the relay in the box above the LHS front wheel that did not energise, and was able to establish that +B was only a couple of volts. I did not trace it back any further.
do you still get the starting fault? It is interesting that even when the car is starting and running ok, the cat light is still on.
Monday, November 29, 2010 - 06:39 pm, by: Malcolm Hall(Neddy)
Hi Tom, thanks for that link. I used to be a field service engineer for an electronics company but it was 25 years ago now so the soldering skills are a bit rusty. That relay that you mention is the main EFI relay and when energised by a signal from the ECM ("M-Rel") it pulls in and feed out a hard 12v from the nearby fuse - this is the "+B" line, so it should be either 0v or 12v, either on or off. The energising signal is where I think my intermittent problem might be but of course it hasn't failed on me for weeks now. I'm thinking that there is something amiss in or around the ECM, like a poor earth or a dodgy connection and this might be affecting the cat warning light too. I might have to hand the car over to a sparkie for further tests but there are not many Soarer specialists in Townsville. I'll repost when I get any further. Cheers!
Monday, November 29, 2010 - 09:13 pm, by: Tom Richards(Tomr)
hi ,malcolm,
in a past life , 30 + yrs ago i was in the RAAF working in electronics. I dont know where the M-REL is generated. I think when it is absent, some leakage gives the couple of volts on the +b line.
I do not think the average sparkie will track it down. Most faults in the soarer ecu's are failed electro caps.
Tuesday, November 30, 2010 - 04:39 pm, by: Aiden Cheese(Chillpen)
Or your cat is falling apart internally but you should be able to tell because when you drive it, it'll be hard to get RPM high up.
Mine fell apart recently and some of the peices of the honeycomb turned ninety degrees causing a massive restriction of flow. Of course that was due to a shudder, but before that shaking the exhaust heard lots of rattles from the cat specifically as it was falling apart.
Here's a tip: even if its a electrical fault, try and give the exhaust a shake anyway if you haven't replaced the cat in your ownership of the car. Rattling noises are bad.
Wednesday, December 01, 2010 - 11:12 am, by: Malcolm Hall(Neddy)
Thanks for that Aiden, I will certainly give the cats a rattle but the engine runs like a dream (as long as the fuel pump runs!), revs freely and there's no sign of choking in the exhaust, or rattles as I drive but I guess you are right - there is always the possibility that the warning light is actually doing its job and warning me of a cat problem...
It's easy to be misled by coincidences: once in my youth with an old Ford both brake lights packed up at the same time. "There must be a common cause" thought I and spent ages checking out the fuses, brake light switch, wiring, earths etc etc - everything in fact except the bulbs. Finally in desperation I took the bulbs out and checked them - both blown. I should have learned but I guess some of us are slow learners
Wednesday, December 01, 2010 - 12:50 pm, by: Aiden Cheese(Chillpen)
Yep no worries, my friends toyota sera had it's exhaust pulled off recently and bits of cat were just falling out. It's about the same age as my car which did the same. But it's pretty easy to tell if the cat is *really* •••• to the point of overheating because it will be lower on power by a fair bit too.
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