I’m looking for technical help or recommendations on: PCM fault
I have had an intermittent fault with engine and traction control lights coming on, car struggling to start and particularly in damp cold weather stuttering. Doesn’t happen all the time, but something definitely wrong. Eventually took to local Mazda garage as independent had no idea. Mazda’s verdict is its a fault with the ‘brain’. This is their email:
‘Fault Engine management and traction control warning lights on.
Connected Mazda diagnostic computer and investigated fault memory. Found fault codes U2023 and P0117 stored in system.
Replaced coolant temperature sensor. Inspected wiring supply of 12-volts and earthing points.
Tested wiring into and out of Powertrain Control module (PCM) This is the main control unit for the vehicle.
Notice 5-volt signal feed to be low from PCM may have a resistor issue in the PCM. Contacted Mazda technical for extra testing advice. The PCM is not currently available.
Next step to contact an electrical company who will test the Powertrain control Module.’
Anyone else experienced this? Does their course of action sound reasonable? Is it possible to obtain a replacement PCM from anywhere if it can’t be fixed?
Thanks in advance for any help or advice you can offer, I will pass it to the garage.
I’ll start with probably stating the obvious…have you checked that the skuttle grommets are watertight ? There’s a known problem of the seals round the fixings perishing and letting water in/under the dashboard/cab on the passenger side where there lies a fusebox/control panel beneath.
If dampness is getting at it, there’s no telling what amount of issues that may cause.
Thanks. I have had a problem with seals and water (ended up with passenger footwell full of water after scrubbing roof before reproofing), I asked Mazda to look at that and they have resealed, so wonder if that could be an issue. I will ask them if they have checked fuse box in that area as not sure what tests they have done. However they have had the car for a couple of weeks to try and narrow down where the fault is, so would hope they have investigated that area
I would link that leak and the electrical gremlins definitely, especially if they happened around the same time.
If left the water can do costly damage to the electrics. Drying out of that small fuse board and associated area can cure your problems. Of course it could be unrelated issues but definitely don’t discount it.
As explained above you would need the black plastic panel at the base of the windscreen removing to check the sealing around the grommets. Do it and seal around them as a matter of course, if they aren’t leaking now they will in future.
Thanks. I’ve been in touch with the garage and they have already looked at that as a possibility and discounted it. They’re going to send the PCM off to a company to check it.