ECU wiring connections

Technical questions and answers about the Mazda Bongo

Moderators: Doone, westonwarrior

Cynog
Apprentice Bongonaut
Posts: 4
Joined: Mon Aug 10, 2020 12:00 pm
Location: Cynon Valley

ECU wiring connections

Post by Cynog » Fri Sep 11, 2020 6:11 pm

I've recently been crazy enough to take on a Bongo which has been VOR for several years following an engine cutting out problem which gradually grew in frequency until it was impractical to drive.
It's a 2.5td AFT 4WD made in November 1999. It starts without problem, but after say 8 minutes of idling the coil lamp starts to flash and a few minutes later the engine cuts out, unless the engine cover is open when it continues to run at least long enough to bleed the cooling system.
The coil lamp flashes uniformly unless I attempt to read the ECU error codes using an earth jumper and a bulb, when both the coil lamp and the bulb flash together, showing codes 11, 12, 14, and 18 (!) if I'm understanding it correctly (definitely not 38). Faults with the engine bay sensor (11) and scavenger system (14) make sense, and the throttle sensor (12) I will need to look at. As the hold lamp flashes occasionally it seems there's probably an intermittent fault there.
My first question is, does fault code 18 exist and if so, what is it?
The second problem is that the ECU terminals don't correspond with the diagram in the manual. My Bongo has 27 wires connected, but spread around 38 terminals, so it's tricky checking for continuity. Does anyone know where I can find details of the later ECU and wiring colours please?
My third problem is that disconnecting both battery earth leads and operating the brake pedal doesn't get rid of the error codes (or the flashing lamps). I have to wait until the engine is fully cold to start again.
The vehicle has a very nice camper conversion and it will be a great Bongo again once I've sorted the engine, brakes and some tin worm. Any advice would be very gratefully received.
willow2u
Bongonaut
Posts: 96
Joined: Tue Jun 30, 2020 2:35 pm

Re: ECU wiring connections

Post by willow2u » Fri Sep 11, 2020 7:36 pm

I would be curious as to why the engine runs longer with engine cover open
User avatar
g8dhe
Supreme Being
Posts: 8793
Joined: Sun Apr 13, 2008 10:06 pm
Location: Worthing, West Sussex.

Re: ECU wiring connections

Post by g8dhe » Fri Sep 11, 2020 8:32 pm

Where are you getting the ECU pinouts from ?
The wiring diagrams I have put on-line are only up to September 1999 so they could have changed in the later versions;
http://www.g8dhe.net/bwm
You will need Flash installed and enabled for the site within the browser.
Geoff
97 V6, AFT, full side conversion.
Image Spherical Visions
rita
Supreme Being
Posts: 3219
Joined: Tue Sep 15, 2009 7:11 pm

Re: ECU wiring connections

Post by rita » Fri Sep 11, 2020 9:58 pm

willow2u wrote: Fri Sep 11, 2020 7:36 pm I would be curious as to why the engine runs longer with engine cover open








Thats a good point, there might be a wee clue here.......


Faults with the engine bay sensor (11) and scavenger system (14) make sense,.
Cynog
Apprentice Bongonaut
Posts: 4
Joined: Mon Aug 10, 2020 12:00 pm
Location: Cynon Valley

Re: ECU wiring connections

Post by Cynog » Fri Sep 11, 2020 10:31 pm

Thanks for your replies. I'm assuming the problem, or at least a part of it, is a faulty scavenging system and having the engine cover open is easing this. As Rita notes, this ties in with the codes.
I've checked the resistances across the engine bay temperature sensor and they are good, as is the 5v supply to it. I've also checked the coolant temperature sensor resistances and they are good too. Disconnecting the coolant sensor causes all radiator fans to run at full speed, so the coolant system seems likely to be okay, although I note the fault arises before the radiator fans have cut in.
I now want to check for a break or a short in the wiring of the scavenging system and without a wiring diagram or details of the ECU connections and colour codes I'm floundering.
Does anyone know whether the reluctance to clear the codes is likely to be down to an error in my method (it seems simple enough) or is it a common experience?
Cynog
Apprentice Bongonaut
Posts: 4
Joined: Mon Aug 10, 2020 12:00 pm
Location: Cynon Valley

Re: ECU wiring connections

Post by Cynog » Fri Sep 11, 2020 10:44 pm

And thanks Geoff. Yes, the ECU I'm dealing with is rather different, though it has occurred to me that by studying the earlier diagrams I can probably get a much better idea of how Mazda wired the control systems than I have so far!
Thank you for all your work on these and I'll see what I can learn this weekend.
Cynog
Apprentice Bongonaut
Posts: 4
Joined: Mon Aug 10, 2020 12:00 pm
Location: Cynon Valley

Re: ECU wiring connections

Post by Cynog » Mon Oct 05, 2020 10:13 pm

Just an update on this problem and a Thank you to all who responded.
I've subsequently made sense of the fault codes. I hadn't realised that the 4-number codes give a long flash to denote the start of each digit in the code, hence I missed the zeros!
When it dawned on me, I realised I had a pesky EGR fault - 0400 and 1228. As blanking gaskets had been fitted at each end of the EGR pipe, I removed and cleaned out both valves with oven cleaner, checked for movement when a vacuum is applied to each, cleaned the ports and pipe, then refitted everything.
I've just run the engine on the drive for an hour without any flashing lights! :D My next job is to sort out the ABS fault showing, a limited amount of rust underneath, and book an MOT. Then I'll discover whether I have cured the EGR fault properly.
Btw I've seen a YouTube video suggesting EGR systems can be cleaned by spraying oven cleaner into the turbo. I strongly recommend not doing this. On worn engines, the ones likely to have EGR problems, the carbon around the top of the pistons will be acting as an extra piston ring. Feeding anything that clears carbon effectively through the engine may shift the carbon out of the EGR but will very likely do the same to the combustion chambers.