First lets clear up the symptoms so we are talking about the same things. "Crank" and "turn over" are the same thing. They mean the starter is cranking the engine. You said it does and it does not. The biggest misconception is the diagnostic fault code. They never say to replace a part or that one is bad, so you should not be trying to replace the oxygen sensor yet. There are over a dozen fault codes related to oxygen sensors, and they mean very different things. Some of those codes are set when a properly-working sensor detects a problem, so replacing the sensor isn't going to solve anything. We need to know the exact fault code number so we can look up its meaning.
While an oxygen sensor could be defective, it is not going to cause a noticeable running problem. The symptoms you described have some other cause, and that is likely to be related to the flashing Check Engine light. The flashing light indicates the most serious of conditions is being detected and you're supposed to stop the engine right away. Forcing the engine to stay running is sending excessive un-burned fuel into the exhaust system where it will burn in the catalytic converter and overheat it. That can turn a minor problem into an expensive repair. Most commonly the excessive fuel in the exhaust is caused by spark-related misfires, typically from worn spark plugs or wires. For engines that use the coil-on-plug ignition coils, a failing coil can cause that too. To identify those, note the cylinder indicated in the misfire fault code, erase it, then switch that spark plug with one from a different cylinder. If the spark plug is the cause of the misfire, a new fault code will set for the cylinder the suspect plug was moved to.
Replacing sensors introduced new variables into the problem. That should only be done if there's a fault code that indicates that circuit needs further diagnosis. Often fault codes don't set for the cam or crank sensors just from cranking the engine. They set easier while a stalled engine is coasting to a stop. If you don't have a fault code related to them, but you suspect one has failed, it is more effective to observe them on the live data screen on a scanner. During cranking, they will be listed with a "No" or "Present" to specify if their signals are showing up to the Engine Computer.
When you don't have access to a scanner, you can tell if those signals are showing up by watching if the automatic shutdown, (ASD) relay is turning on. The Engine Computer turns that relay on when the engine is rotating, (cranking or running), and it knows that by those two sensor signals. Find the wire that is the same color at the ignition coil(s), every injector, or either small terminal on the back of the alternator. That is usually a dark green / orange wire. Back-probe that through the rubber seal, with a test light. Digital voltmeters don't respond fast enough. You should see the test light turn on for one second when you turn on the ignition switch. You might be able to hear the hum of the fuel pump at the same time. What is important is the light should turn on again during cranking. If it doesn't, those two sensors and their wiring are suspect. If it does, the sensors are working, and you have an ignition system OR fuel supply system problem, but not both. The sensor circuits account for about 95 percent of crank / no-start problems. You'll have no spark AND the fuel pump won't run during cranking. The fuel pump accounts for about another four percent, and one percent are caused by the ignition coil or coil pack.
There are special sockets made for removing oxygen sensors. If you're going to replace an O2 sensor, it doesn't matter if the old one is broken while removing it. On rare occasions one might be rusted tight enough that coupled with poor accessibility, it might be too tight to loosen. For that, visit the Chrysler dealer's parts department and ask for a spray can of their "Rust Penetrant". Squirt a little of that in the area of the threads, then wait about ten minutes. This stuff will do in ten minutes what WD-40 will do in a weekend. It was originally intended for rusted heat-riser valves on '60s through '80s engines.
Do you know how to read the diagnostic fault codes yourself?
Friday, March 24th, 2017 AT 5:04 PM