When a Crankshaft-Camshaft Position Sensor goes BAD, your vehicle will not start.
It’ll crank but not start.
A car (or truck) could not start due to a ton of different reasons like:
- A BAD Fuel Pump
- BAD Ignition Coil
- A BAD Ignition Control Module
- BAD Spark Plug Cables, etc.
A failing Crankshaft-Camshaft Position Sensor can produce a confusing range of problems, depending on the type of failure and the type of car:
- Transmission locking in a single gear until you turn it off and restart
- Car jerking and losing power
- Loss of engine power; for example, no acceleration above 35 mph
- Irregular acceleration
- Hard starting
- No spark: no start at all
- No Fuel Injector Pulse
Another thing that can make testing the Crankshaft-Camshaft Position Sensor seem intimidating is the fact that every make and model uses a different type of Position Sensor. Therefore, it’s not enough to say that your car or truck won’t start, what you need to know are some of the measurable/testable effects/symptoms that a BAD Crankshaft-Camshaft Position Sensor has on the Ignition System.
Not only that, but these sensors are called by so many different names like:
- Hall Effect Sensor
- CKP Sensor
- CMP Sensor
- Pickup Coil
- Magnetic Pulse Generator
- Variable Reluctor
This may make it seem like every single one is tested in a different way.
Well, the good news is that although they all differ from one another physically and are called so many names, they can usually be generalized into two basic categories:
2 wire type
3 wire type
I want to emphasize that the key to successfully testing and diagnosing all of the different Crankshaft-Camshaft Position Sensor out there, is to know if they are either a two or three wire type!
Now in case you’re wondering what I mean by two and three wire types… I’m referring to the amount of wires in their connector (of course there’s always an exception to every rule).
If your car computer has already triggered the engine light, you may retrieve the code (the DTC) using a code reader or a relatively inexpensive scan tool. If you don’t own a code reader and can’t afford to buy one, and you still can drive your car safely, just go to a nearby auto parts store that retrieves DTCs for free.
After confirming a Crankshaft-Camshaft Position Sensor related trouble code, it’s worth doing some simple tests. A trouble code pointing to a potential Crankshaft-Camshaft Position Sensor failure doesn’t necessarily mean that the sensor itself is bad. You may be dealing with a wire, connector, or related component failure that you can fix yourself.
However, confirming the good or bad operation of a Crankshaft-Camshaft Position Sensor may require a scope. A failing sensor signal, for example, may be hard to check without special equipment.
Still, you can do some simple checks in your garage using a digital multimeter (DMM) tool.
- First, check the condition of the sensor’s electrical connector and wires. Unplug the connector and check for rust or contamination, like oil, that is interfering with good electrical contact. Then check for wire damage: broken wires, loose wires, and signs of burns caused by nearby hot surfaces. Also, make sure the sensor wires are not touching spark plug wires or ignition coils, which may interfere with the sensor’s signal.
- After these checks, use a digital multimeter that can test either alternate current (AC) voltage or direct current (DC) voltage, depending on your particular type of Crankshaft-Camshaft Position Sensor. You’ll also need the correct electrical values for your particular type of sensor. You may find this information in your vehicle repair manual.
- With some sensors, you may backprobe the wires through the sensor electrical connector. If this isn’t possible, see if you can unplug the sensor connector and attach a strand of copper wire to each terminal on the connector. Then, plug the connector back in so that the two strands stick out through the connector’s housing. Another solution is to pierce through each wire using a pin, being careful not to short out the wires during your tests. If you use this last method, use electrical tape to cover the pin holes on the wires’ insulation after you’re done with your tests to prevent corrosion from creeping into the wires.
Testing a Two-Wire Sensor:
- If you have a two-wire, magnetic-type sensor, set your multimeter to “AC volts.”
- Have an assistant turn the ignition key on without starting the engine.
- Check for the presence of power flowing through the circuit. Touch one of your probes to ground (any metal part on the engine) and the other probe to each one of the sensor wires. If neither wire has current, there’s a failure in the sensor’s circuit.
- Have your helper crank or start the engine.
- Touch one of your meter probes to either one of the sensor wires and the other probe to the other wire. Check your meter display and compare your reading to your manual specifications. In most cases, you’ll see a fluctuating signal between 0.3 volts and 1 volt.
- If there’s no signal, you have a bad sensor.
Testing a Three-Wire Sensor:
- Once you identify the power, ground, and signal wires using your vehicle repair manual, test the sensor’s circuit by setting your multimeter to “DC volts.”
- Have your helper turn the ignition key on, but don’t start the engine.
- Touch the black probe on your meter to ground (a metal bracket, bolt, or metal surface on the engine itself) and the other probe to the power wire. Compare your reading to the specification in your manual.
- Have your helper crank or start the engine.
- Touch the signal wire with the red probe from your meter and the ground wire with the black probe. Compare your reading to the specification in your vehicle repair manual. If the voltage signal is lower than the specification, or no signal comes out of the sensor, most likely the sensor is bad.
- Remove the sensor and inspect it for signs of physical damage or contamination.
If you can’t find anything wrong with the Crankshaft-Camshaft Position Sensor or its circuit, it’s possible you may have an intermittent failure or a failure in a related component. For example, you may have a weakened or overstretched timing belt or timing-belt tensioner.