Sorry to disagree with Tristan but changing the crank shaft sensor is relatively easy. Changing the cam sensor is slightly more involved.
Here's how to check the cam sensor and how to change both of them:
Check Cam Sensor:
1. Remove black cover along top of engine using 5mm allen key.
2. Cam sensor is at front of engine. There are 2 types of connector, rectangular and oval.
3. Remove the connector by pushing the metal release bar on the rectangular type or pressing the plastic release tab on the oval type.
4. Measure the resistance of the sensor's coils. Coil 1 should be about 12 ohms between pins 1 & 2 and coil 2 about 0.5 ohms between pins 2 & 3. Pin 1 is nearest the radiator.
5. If the resistance of coil 1 is much more than 16 ohms it is suspect. If coil 2 is much more than 3 ohms it is suspect.
6. If the resistance seems correct try heating the sensor with a hair drier to get it hot and measure them again. The fault may only occur when the sensor has been heated by the engine.
7. If the sensor is measuring high or even open circuit (I've seen both) then it must be changed. Obtain a new one and check it's resistance before fitting it!
8. If your old sensor was the rectangular connector type you may find that your new one has a different connector. It should also be supplied with a length of loom with the correct plug on the end. If you have access to an AMP crimp removal tool you can simply swap the housings over. Pins: 1 - grey/black, 2 - grey/red, 3 - green/brown.
9. If you cannot do this (most people will not) then your only option is to cut your existing loom at a sensible point and splice in the new one. I suggest soldering and sleeving the connections. The screen wire does not need to be sleeved, just solder the two ends together and then wrap the joint with some aluminium foil. Slide a piece of heat shrink sleeving over the entire joint to insulate it. You could use insulation tape if that is all you have. The joints must be reliable otherwise you will be back to square one!
Changing Cam Sensor:
1. Remove the air cleaner and the rubber inlet hose up to the joint after the MAF sensor.
2. Remove the engine front stabiliser (15mm & 16mm bolts). There is no need to support the engine.
3. Remove the driver's front road wheel.
4. Using a 15mm socket on a ratchet, release the V belt tensioner and unhook the belt off the alternator pulley.
5. Remove the cam belt cover (3 x 10mm bolts). Do not loose the plastic inserts!
6. Carefully manoeuvre the cover off.
7. Using a suitable socket remove the small torx bolt securing the cam sensor in place. The sensor then lifts out vertically.
8. Fitting is the reversal of removal. Before doing so you might want to check the condition and tension in the cam belt. The tension is indicated by a pointer on the belt tensioner. It should be aligned with either the left hand mark (used belt) or the right hand mark (new belt). Check that the water pump is not leaking and that the pump bearing is not badly worn.
9. After reassembly the engine should run and the warning light will be off. The fault code will still be logged in the ECU and can be removed with a Tech-2 type OBD reader. This is not essential for the repair to take effect. It is an urban myth that the code must be cleared as well as fixing the fault for the warning light to go out!
10. Job takes about 1-2 hours.
Sensor Measures OK:
1. If it still measures OK then measure the resistance from the ECU. On the 2.0 Ecotec it is mounted in the scuttle above the passenger's front foot well. The ECU is accessed from the engine bay by removing the rubber seal strip along where the pollen filter is fitted.
2. There is a large rubber boot covering the ECU held on with 4 x 10mm nuts. Once these have been removed, carefully lift the rubber boot to reveal the ECU connector.
3. Lift the connector from the ECU. Make sure that the sensor is plugged back into the loom. Coil 1 is between pins 13 & 31 and coil 2 between 32 & 31. You may need an assistant to 'wiggle' the loom to determine if there is a break in the loom.
4. If the resistance is changing then you will have to track down the break in the cable and fix it.
Changing the Crank Sensor:
1. If for some reason you need to change the crank sensor, here are some tips.
2. Remove the dip stick and dip stick tube. This may be aided by removing the power steering pipe stay (torx head screw).
3. Working from under the front of the engine unbolt the torx screw (8mm ring spanner or socket) that holds the sensor in place.
4. If the sensor cannot be pulled out easily, rotate it to and fro and if it still will not come out use a wide bladed wood chisel to carefully lever it out.
5. Trace the loom from the sensor and disconnect the 3 pin plug and socket. Tape a piece of scrap wire to the plug on the sensor side of the loom and pull the sensor and its loom out from the dip stick side of the engine. The scrap wire is to help pull the new sensor's loom back through.
6. Reassemble with the new sensor carefully manoeuvring the connector back through the gap behind the power steering pump.
7. Job takes about 45 mins.
Kevin, October 2007
