Jeep won’t start or Jeep starts and stalls
There are many reasons why a Jeep won’t start or Jeep starts and stalls. But if you have a check engine light on a 2000-04 Jeep with 4.0L engine and you scan the trouble codes, you may find any of these trouble codes:
P0340 No Cam Signal At PCM
P0351 Ignition Coil # 1 Primary Circuit
P0352 Ignition Coil # 2 Primary Circuit
P0353 Ignition Coil # 3 Primary Circuit
Do NOT start replacing ignition coils!! They would not be the root cause of the problem.
2000-04 Jeep with 4.0L engine
Jeep won’t start or Jeep starts and stalls indicates a camshaft position sensor issue
Jeep uses the camshaft position signal to trigger the timing and firing of the fuel injectors. It uses the crankshaft position signal to fire the ignition coils. If the crankshaft and camshaft signals are out of synch with one another, or the sensors have failed, you’ll get a Jeep won’t start or Jeep starts and stalls condition.
Diagnose and fix a Jeep won’t start or Jeep starts and stalls condition
The correct way to diagnose this is with the use of a scope. Most of you probably don’t own one, so here are some tips. The camshaft position sensor on these 4.0L Jeeps from the early 2000 era sit on top of what used to be the distributor. The timing chain drives the camshaft and a gear on the end of the camshaft drives the distributor shaft. The shaft is also keyed to the oil pump and that’s what drives the oil pump.
Since distributors were designed to be rotated to bring the engine into correct timing, these distributor camshaft position sensor adapters are also designed to rotate to properly align the camshaft position sensor. If the hold-down bolt has loosened or anyone has attempted to rotate the housing, the camshaft position sensor will be out of synch with the crankshaft position sensor and will cause this condition.
Check the hold down clamp and bolt for any indication that
someone has attempted to rotate the distributor housing. If not, then you can suspect either the crankshaft or camshaft position sensor.
The problem is determining which sensor is bad without having a scope.
If you have a digital voltmeter, you can at least test the 5-volt reference signal coming to each sensor and ensure each sensor has good ground. If you don’t have those, then you’ve got a fuse, wiring or PCM issue. If you do have those, then you can be a bit more comfortable replacing the sensors.
Test crankshaft position sensor
Remove the electrical connector from the crankshaft position sensor and connect your digital meter in this fashion. Turn the key to RUN.
Test camshaft position sensor
Remove the electrical connector from the camshaft position sensor and use a digital meter to check for 5-volt reference and ground as shown in the image.
©, 2017 Rick Muscoplat
Posted on by Rick Muscoplat