I put a call out to a friend who rebuilds smashed Chrysler products. He will know if they are using this system on your truck. You need to list the engine size though since we're talking about an engine problem.
The code suggests the signal is coming from a three-wire sensor similar to a throttle position sensor. If that is right, or until I know better, we can diagnose it the same way. Those sensors are fed with 5.0 volts from the Engine Computer. The ground wire goes to ground but it goes through the computer to do that so that circuit can also be monitored. When it is working properly, the sensor has mechanical stops that allow the signal voltage to go from 0.5 to 4.5 volts, (approximately). The signal voltage can never reach 0 or 5.0 volts. If it does, that is what triggers the code, and it has to be due to an electrical problem.
If the ground wire is open, the full 5.0 volts will appear on the signal wire and that will set the "high" code. You will find 5.0 volts on the sensor's ground terminal too but you have to back-probe the connector to take that reading with the connector plugged into the sensor. It is very uncommon but the ground terminal can be broken inside the sensor too. That will result in a high signal voltage all the time but it will also result in 0.0 volts on the ground wire. Normal is 0.2 volts and that's what shows that circuit is okay.
You can also set this code if the signal wire is open, or more commonly the wiper has an intermittent contact due to dirt. When that signal circuit has an open circuit, the voltage can "float" to some random value from what people call "back-feeding" from being interconnected to other circuitry in the computer. It's possible for the voltage to float to something between 0.5 and 4.5 volts and the computer will try to run on that, so to prevent that incorrect floating voltage they use a "pullup resistor" tied to the signal terminal inside the computer. Pull-up resistors are so extremely high in value that it's like they aren't even there when the circuit is working properly, ... But when there is a problem they force the voltage to go to 5.0 volts so the problem will be detected and a code will be set.
The best way to tell if the circuit is working is to connect a scanner to view live data, then watch the sensor's voltage as you move the linkage to the valve. It should go smoothly from 0.5 to 4.5 volts with no momentary dropouts to 0.0 or 5.0 volts. Scanners respond much slower to those readings than the computer does so it's easy to miss them.
The alternative method is to measure the signal voltage with a digital voltmeter. Again, that has to be done with the plug connected, otherwise there will be that open circuit and the voltage will go to 5.0 volts. You should read a nice smooth sweep from 0.5 to 4.5 volts, (approximately) as you move the linkage. By "approximately" I mean you might find 0.36 to 4.23 volts or something like that. The point is it must never get close to 0.0 or 5.0 volts. If you pull the connector off while the ignition switch is on you'll find 5.0 volts on the signal wire, and that will set the code.
Typically one of two things is going to happen. You will find 5.0 volts on the signal wire all the time or you're going to find the proper 0.5 to 4.5 volts all the time. For 5.0 volts all the time you have a definite problem that can be diagnosed with an ohm meter or voltmeter. There's a 50 percent chance it is caused by a broken wire and a 50 percent chance it's caused by a break in the sensor.
If you find the correct 0.5 to 4.5 volts as you move the linkage, that proves the sensor, 5.0 volt feed, and ground wires are okay. If the signal wire is open you'll still see the normal range of voltage at the sensor with a voltmeter but a scanner will show 5.0 volts at the computer. If you see the proper range of voltage at the computer with a scanner, that proves everything is working and the computer detected an intermittent glitch from the sensor. That is usually due to dirt inside the sensor and replacing it is in order.
We never condone replacing parts as a guess or as a test unless diagnosis points to that because that can introduce more variables into the problem, but in this case if you found the diagnostic steps hard to follow, or if that isn't a three-wire sensor, you may want to put a new one on and erase the code, then see if that takes care of it. If the code comes back right away, there is a wiring problem. If it takes hours or days of driving before the code comes back, suspect a corroded splice in a wire, a stretched or corroded terminal in a connector, or something like that that's causing an intermittent connection.
Saturday, October 20th, 2012 AT 8:21 PM