Any time an Australian-made Ford of this vintage has a problem with its door locks, suspicions will turn to the car’s body computer. This is a known fault in these vehicles and will probably require a new body computer as well as somebody who knows what they’re doing to fit it.

The body computer controls all sorts of functions including the wipers, light, security system, climate control, entertainment system, and the central locking.

But before you book the car in to the auto electrician, try this: Disconnect the battery and leave it overnight. Next morning, reconnect the battery and see if that has sorted the problem. In some cases, this will reset the computer (kind of like a return to factory settings function) and the car will work properly again. Sometimes it works, sometimes it doesn’t and the results aren’t always permanent. But it’s free and definitely worth a try.

This is a pretty common fault on modern cars and it will usually lead a mechanic to one line of enquiry. And that is a check of the fuel pump.

Electric fuel pumps have a finite lifespan and when their time is up, they just stop. So the next time you try to start the car, it will turn over normally, but there’s just no fuel getting to the engine.

So try this: turn the ignition key until you get dashboard lights and then listen carefully. You should be able to hear a faint buzz or thrum that is the sound of the fuel pump whirring away. If you can’t hear it, that’s a strong suggestion that it has died. The other thing to try – if you’re a bit more mechanically minded – is to disconnect the engine’s intake trunking and spray some starter fluid down the engine’s throat. If it fires and then dies straight away (once the starter fluid has been consumed) you’re definitely looking like a new fuel pump is in your future.

This problem could also be about a hundred other things, of course, but eventual fuel pump failures on cars like yours are about as certain as death and taxes.

You’ve probably already figured out that the two codes mean you potentially have two separate problems, but either one of them could cause your car to switch to limp home mode. In any case, they both need to be fixed.

So, let’s start with the PO118 code. This suggests you have a faulty engine coolant temperature sensor. When this fails, the computer isn’t getting the information it needs to know whether the engine is cold or warmed up. As a result, the fuel-air mixture will be all over the place and the vehicle will possibly use more fuel and run poorly as well as being hard to start in the morning.

The other fault code you’re seeing, PO489, is to do with the engine’s exhaust gas recirculation valve. This valve channels some of the engine’s exhaust back through the combustion chambers to reduce tailpipe emissions by burning the same gasses twice. Your car’s computer will be constantly opening and closing this valve, but it’s an electrical signal (from a sensor) that tells it when to do so. If this sensor has failed, that information won’t be getting sent to the computer and the check-engine light will come on.

Both of these faults will probably be fixed by replacing the sensors in question, but until they are replaced, the car will continue to throw fault codes and switch to limp home mode.