Yes you do. The flashing Check Engine light. The Engine Computer tested the sensors for you.
37 - Part throttle unlock (PTU) circuit, open or short detected.
The only problem is in the way the fault codes are set. It is easier to describe the throttle position sensor. It is fed 5.0 volts and ground. (Actually there's 0.2 volts on the ground wire, but that is not critical to this sad story). The movable wiper picks a voltage between those values, lower at idle and higher at wide-open-throttle. The important detail is there are mechanical stops inside the sensor that prevent it from going below 0.5 volts or above 4.5 volts. Anything outside that range is what triggers a fault code. The TPS is a mechanical sensor, and a signal voltage of 0 or 5.0 volts will only be seen if there is a break in one of the wires or one of the connections in that circuit.
The MAP sensor sets a fault code if the same readings are seen outside the acceptable range, but there are some important differences. This is an electronic sensor with a lot of circuitry inside it. That makes it susceptible to more than just wiring problems. A circuitry problem can cause it to develop the wrong signal voltage.
Understand that the 0.5 to 4.5 volt range in my story is for explaining theory. In practice, if you were to measure the voltages with a digital voltmeter, or look at them on a scanner, you might find 0.38 and 4.58 volts, for example. The actual numbers are not that important as long as they do not get close to 0.0 or 5.0 volts.
With a vacuum leak or an internal circuitry problem, the MAP sensor can send the wrong signal voltage, but as long as it remains within the acceptable range, no fault code will be set. At that point the mechanic has to view the signal voltage and try to determine if it looks right based on the readings from the other sensors. Chrysler is the only manufacturer that has been able to make their engines run right with just the MAP sensor. Other manufacturers need a mass air flow sensor for their main fuel metering calculations. The MAP sensor is the most important sensor on your truck.
One test that might provide some insight is to unplug the MAP sensor. The Engine Computer will see 5.0 volts, set a fault code, and since it knows it can't use that signal, it will inject an approximate voltage to run on, based on the other sensors' readings and operating conditions. The engine will not run well, but if the symptoms improve, the sensor and its circuit become good suspects.
Also, consider removing the EGR valve and reinstalling it with a thin metal shim to block the ports. If the rough running clears up, suspect the valve is not closing fully. Remember the EGR is supposed to open at highway speed, so it will not cause rough running then.
Tuesday, January 17th, 2017 AT 4:47 PM