Ford Focus Ghia 1.6 2006 - Check Engine Light and Alarm

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Sun 4 Dec 2011 13:26
Ford Focus Ghia 1.6 2006 - Check Engine Light and Alarm - IKM

I recently had the check engine light come on flashing and the engine running rough. I drove home, about 30 miles then put the car into a local independent garage. A faulty coil pack was diagnosed, using a computer hooked up to the car, and replaced. The car is now running well but the check engine light is now on steady at all times when the ignition is on. The mechanic tried to reset it using the computer without success because the oxygen sensors are indicating an emissions fault. He suggested to leave it for a few days then try the car on the emissions tester if the light is still on. I suspect that the catalytic converter and or sensors may be affected by the unburnt fuel due to the misfire. I've have done about 20 miles over 2 days since the coil pack was replaced and the light is still on. Does anyone have any ideas on this?

Since the coil pack was replaced and the attempted reset of the engine light the alarm has also been affected. A few seconds after switching off the ignition a warning is diplayed that the interior alarm has been deactivated. A few hours after locking the car the main alarm becomes disabled and the car can only be opened by using the key in the lock. It seems like the car is in a factory mode where the alarm is automatically disabled after a period to prevent false alarms and discharged battery during transort and storage. I sure I can get this fixed relatively easily by a ford dealer but if anyone knows a home fix please advise.

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Fri 30 Dec 2011 11:50
Ford Focus Ghia 1.6 2006 - Check Engine Light and Alarm - IKM

In case it helps anyone in the future I can now update on the resolution to the two problems in my original post. The car is a Mk ll Focus Ghia with the 1.6L Ti-VCT 115PS engine.

Check Engine Light: The CEL didn't go out on it's own so after about 1 week I returned the car to the garage for further investigation. They cleaned the spark plugs, checked the exhaust emissions and found them to be OK to MOT requirements, then reset the CEL to off. However at the next engine start the light came back on. (I later found out that it takes two engine start cycles for this fault to be registered by the engine management computer.) I decided to investigate myself and found that the wiring of the Heated Oxygen Sensor No. 2 (the after-CAT sensor) on Bank 1 (for cylinders 1 and 2) of the catalytic converter had made contact with the CAT, burning throught the insulation resulting in an intermittent short circuit between one of the sensor heater wires and chassis. Fuse F33 (10A) in the engine fuse box was blown. I found that on this car F33 supplies +12V to the heaters on all four oxygen sensors and not just two of the four as stated in the Owner's Guide supplied with the car. Also, the fault codes generated by this fuse blowing relate only to the two pre-CAT sensors.

The reason for the sensor wiring touching the CAT was a combination of the wiring support bracket broken due to corrosion, the CAT heat shield falling down due to corrosion at the fixings, and general movement of the wiring during the investigation of the misfiring fault.

I have made a temporary fix by cutting the 4 wires to the sensor in order to thread insulating sleeving over the burned wires, rejoining the wires, then tying up away from the CAT. I replaced the 10A fuse and reset the CEL using a U480 OBD ll Diagnostic Scanner tool, bought from an ebay seller for about £18. The light remains out after about a weeks running.

Alarm Fault: This problem fixed itself after a few days. I don't know why I'm but pleased to accept that I can open and close the doors again using the remote key fob.

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