Where are you measuring this five volts? One wire on the sensor is fed with 5.0 volts, and another one is the ground, which will actually have 0.2 volts. It's the signal wire in the center the Engine Computer looks at. There's mechanical stops inside the sensor that limit its travel to approximately 0.5 volt at idle to 4.5 volts at wide-open-throttle. Those voltages are approximate. On yours, you might find 0.38 and 4.25 volts, for example, but you'll never get to 0.0 or 5.0 volts.
The only way to get 5.0 volts on the signal wire, which is what triggers that code to set, is to have a break in the ground circuit or the signal wire circuit. The thing you must be aware of is those breaks can be inside the sensor, but it's much more common for it to be in the wire or the connector terminal. When mechanics diagnose this type of fault code, they do electrical tests on the circuit before spending your money on a part.
To be valid, these readings have to be taken with the sensor connected, so you'll have to back-probe through the rubber weather-pack seals in the connector. If you find 5.0 volts on the ground wire, you're going to find it on all three wires. That can only be due to a break in that wire. That isn't too common because it only goes a short distance before it splices into the ground wires for some other sensors.
The fastest way to test this sensor is to measure the voltage on the signal wire. If that goes from around 0.5 to 4.5 volts from idle to wide-open-throttle, it can only do that if the 5.0 volt feed and ground wires are okay, so there's no need to waste time checking them. The sensor is okay too. Now, if you're reading 5.0 volts on a scanner's live data display while you measure 0.5 volts at the sensor, there is a break in the signal wire going back to the computer. Due to the signal wire being interconnected to all the other circuitry inside the computer, the voltage could "float" to some random value, and if it's between 0.5 and 4.5 volts, the computer will see that as an acceptable value and try to run on that. To prevent that and to force it to set a diagnostic fault code, there is a "pull-up" resistor in the computer to put 5.0 volts on that terminal. That resistor is so big electrically that it won't have any effect on a properly-working circuit, but with a break in the signal wire, it will make it set the code "voltage too high". The clue, as I started to describe, is you'll see an acceptable range of voltage at the sensor, but the scanner will show that the computer is seeing 5.0 volts.
Saturday, October 17th, 2015 AT 9:03 PM