Intermittent starting issue

There is an intermittent non-starting issue when the keyless start button is pressed on my 2011 Ford S-MAX 2-litre diesel – nothing happens! There is also occasionally a MIL and “Engine Malfunction” message appearing on the dashboard but no-fault codes showing when I carry out an OBD check.

I have checked all fuses, relays, the keyless start button connections at the PCM (ECU) and most of the wiring but now suspect the PCM (ECU) may be holding the start off for some reason?

As a temporary measure I have installed a start button that takes live from the battery and puts it straight on to the starter motor solenoid and then with the keyless start button turned on (ignition on), the engine starts and runs with no issues.

I have done numerous OBD checks using an Autel Maxisys MS906BT and, after clearing all errors and road-testing, no errors show – but the Engine Malfunction message will still sometimes re-appear. This, like the keyless start button issue, is very intermittent.

I have checked the keyless start button and the wiring is supplying 12 volts to two of the terminals; and the button itself when checked with a DVM seems to be functioning correctly.

My thinking now is that the issue is in the PCM (ECU) and perhaps it needs to go away for repair – would you agree? Although this could be quite costly (£250-plus, I believe).

Also, would you know where I can get a wiring diagram for the starting circuit? The Haynes manual doesn’t have the starting circuit for this vehicle. Am I correct in thinking that the keyless start wiring (output sides) goes to the PCM (ECU)? Tom Harrington Thanks to Autodata I have found a common fault that causes this problem on the S-MAX and this may well be applicable to your vehicle. The problem is water ingress in the wiring loom, which then causes its failure. The failure occurs at the three-way junction in the engine wiring harness and the insulation should be removed from this area to check for any cracked wires.

There is a loom repair kit part number 1 736 825 to address the problem of any failed wires.

The wiring diagram I have, which is supplied by Autodata, shows that the start/stop button is connected directly to the keyless-entry module, and the connection then comes from the module to the starter relay, so if the button is good and if the wiring problem as above isn’t present, it would be likely that the keyless-entry module may be at fault.

Obtaining information for vehicles is one of the modern problems. Autodata do have a starter circuit wiring diagram but this is a subscription service. The Ford manual I have doesn’t have the wiring diagram and would appear that this is only available to main dealers via an internet link.

I have, though, checked with Haynes. I don’t know which manual you have, but they do assure me that in manual number 6299 – which is the one for your vehicle – the wiring diagram for the starting circuit should be on page 12.30.