Automatic gearbox fault

Technical questions and answers about the Mazda Bongo

Moderators: Doone, westonwarrior

SteveG
Junior Bongonaut
Posts: 24
Joined: Fri May 01, 2020 8:32 am
Location: Essex

Automatic gearbox fault

Post by SteveG » Wed Aug 19, 2020 10:51 pm

My 1995 Bongo diesel automatic has just developed a very bad habit! At around 55mph it will suddenly drop a gear or two for a couple of seconds with a flash from the glow plug light before changing back up to top. This is not a regular occurrence, but very annoying when it happens.
I have changed the ATF and cleaned the filter as per the very good link on this forum. No difference.
The gearbox performs well and does not "kick down" on uphill climbs. There are no noises and no leaks.
Other possible factors may include an intermittent rev counter and recent work which included a diesel pump replacement and coolant system work.
Otherwise the van is brilliant!
Thanks in anticipation
Steve from Essex
willow2u
Bongonaut
Posts: 96
Joined: Tue Jun 30, 2020 2:35 pm

Re: Automatic gearbox fault

Post by willow2u » Thu Aug 20, 2020 8:05 am

Sounds like a solenoid problem
Ian
Supreme Being
Posts: 5462
Joined: Wed Jun 09, 2004 2:47 pm
Location: Bongo Mission Control

Re: Automatic gearbox fault

Post by Ian » Thu Aug 20, 2020 8:26 am

Yes, sounds like solenoid problem. Might as well replace the lot while you are at it. Not cheap though:

https://mazdabongo.com/product/mazda-bo ... p-to-1999/
668. The Neighbour of The Beast.
SteveG
Junior Bongonaut
Posts: 24
Joined: Fri May 01, 2020 8:32 am
Location: Essex

Re: Automatic gearbox fault

Post by SteveG » Thu Aug 20, 2020 8:57 am

Thanks guys. Whatever it takes!
I think I will try to get error codes (via flashing lights???) to confirm. Is there a plug in code reader for this type of vehicle?
User avatar
g8dhe
Supreme Being
Posts: 8791
Joined: Sun Apr 13, 2008 10:06 pm
Location: Worthing, West Sussex.

Re: Automatic gearbox fault

Post by g8dhe » Thu Aug 20, 2020 9:16 am

No plug in code reader, you need to count the flashes from the diagnostic socket, exact details depends on year but 1995 would be as given on the factsheet or on this site http://www.philmcfadden.co.uk/MazdaDiagnosticBox.htm
Geoff
97 V6, AFT, full side conversion.
Image Spherical Visions
SteveG
Junior Bongonaut
Posts: 24
Joined: Fri May 01, 2020 8:32 am
Location: Essex

Re: Automatic gearbox fault

Post by SteveG » Thu Aug 20, 2020 12:35 pm

Have no joy trying to get a code. Does the bulb have to be 12v LED?
Bob
Supreme Being
Posts: 14450
Joined: Wed Oct 17, 2007 12:54 pm
Location: North Somerset

Re: Automatic gearbox fault

Post by Bob » Thu Aug 20, 2020 12:58 pm

Geoff will know, but I would think just an ordinary bulb, not led.
User avatar
g8dhe
Supreme Being
Posts: 8791
Joined: Sun Apr 13, 2008 10:06 pm
Location: Worthing, West Sussex.

Re: Automatic gearbox fault

Post by g8dhe » Thu Aug 20, 2020 1:33 pm

No in fact I would suggest not using LED's as they are polarity conscious so you have to get it round the right way, I suggest a LOW power filament lamp is easier! You need to put in the right link wire obviously for the computer involved and the lamp in the right pins.
Geoff
97 V6, AFT, full side conversion.
Image Spherical Visions
SteveG
Junior Bongonaut
Posts: 24
Joined: Fri May 01, 2020 8:32 am
Location: Essex

Re: Automatic gearbox fault

Post by SteveG » Thu Aug 20, 2020 1:36 pm

Thanks...will keep trying!
SteveG
Junior Bongonaut
Posts: 24
Joined: Fri May 01, 2020 8:32 am
Location: Essex

Re: Automatic gearbox fault

Post by SteveG » Thu Aug 20, 2020 2:24 pm

OK. So I am getting nothing from the "reader" socket having tried all combinations and instructions available in the link. I have tested the bulb holder on the battery and the +B/ground on the socket. All good. I have tried paper clips and different gauge wires to no effect and I assume that I will get some sort of light even if there is no code? The wires at the back of the block all seem to be ok.

I have the option to buy the solenoid pack but would prefer to go armed with a code to pinpoint the exact problem.

Did Mazda have a reader that plugged into this block?
User avatar
g8dhe
Supreme Being
Posts: 8791
Joined: Sun Apr 13, 2008 10:06 pm
Location: Worthing, West Sussex.

Re: Automatic gearbox fault

Post by g8dhe » Thu Aug 20, 2020 2:46 pm

Is either the Glowplug or Hold lights flashing, if not then there isn't an error code! Sounds like its internal to the gearbox and could be the solenoid pack.
The solenoids open valves which allow oil thru to activate the gears/ changes, if its all working electrically then probably there won't be an error to report, however if the oil is blocked or the valve itself has failed then no errors will show up.
Have you checked the condition of the ATF oil using the right procedure https://www.allansvehicleservices.co.uk ... +Check.pdf
Geoff
97 V6, AFT, full side conversion.
Image Spherical Visions
SteveG
Junior Bongonaut
Posts: 24
Joined: Fri May 01, 2020 8:32 am
Location: Essex

Re: Automatic gearbox fault

Post by SteveG » Thu Aug 20, 2020 3:04 pm

Yes, I get a glowplug flash as the gearbox kicks itself down. I used the guide you kindly sent last week to change the ATF and clean out the filter.
I will go for the solenoid pack.
Thanks for your help.....will report back when done.
User avatar
g8dhe
Supreme Being
Posts: 8791
Joined: Sun Apr 13, 2008 10:06 pm
Location: Worthing, West Sussex.

Re: Automatic gearbox fault

Post by g8dhe » Thu Aug 20, 2020 3:49 pm

Ah the error codes are only present whilst the light is actually flashing, if the error clears then the light will stop flashing.

Ah just seen the bit about the intermittent rev counter, that will also cause problems, the TCM needs both road speed and engine speed to know what gear to use.
Geoff
97 V6, AFT, full side conversion.
Image Spherical Visions
SteveG
Junior Bongonaut
Posts: 24
Joined: Fri May 01, 2020 8:32 am
Location: Essex

Re: Automatic gearbox fault

Post by SteveG » Thu Aug 20, 2020 4:56 pm

I had just ordered the new crank sensor. Didn't realise that it could effect my gearbox.....makes complete sense and cheaper than solenoid pack!
Thanks.
willow2u
Bongonaut
Posts: 96
Joined: Tue Jun 30, 2020 2:35 pm

Re: Automatic gearbox fault

Post by willow2u » Thu Aug 20, 2020 7:25 pm

Would think that if it was a crank sensor it would go down generally when hot then work again once it’s cooled down rather than randomly intermittent had a Peugeot auto once you could be Cruising along in top then bang it would drop down a gear engine screaming we would have to stop and switch ignition of then it would restart and top would work again until it dropped out again it had no definite period of time till it happened again it was random in the end I bought a complete auto box of a later model with the AL4 gearbox and swapped the solenoid box completely worked perfectly then