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  • Stock APPS Sensor Voltage Adjustment

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    Stock APPS Sensor Voltage Adjustment

    I just had a wonderful phone conversation with Rburks this morning and his chasing his problems with his idle well he happens to mention the fact he did the APPS sensor voltage adjustment and I like "OMG not again!" There is an article on the Internet that is written up wrong and need to be corrected and/or stopped being used.

    To clear this up more... (The best I can)

    The fact is that the stock APPS sensor is a rheostat yes. But APPS sensor is set at a particular voltage for the electronic switches inside that reports to the ECM if it at IDLE or THROTTLING. If the APPS sensor voltage rises above the voltage listed on the tag the switch changes to THROTTLING. Then when the voltage drops BELOW the voltage on the tag then the ECM switches to IDLING. This means the APPS sensor voltage is disregarded and idling software of the ECM takes over control of the Bosch VP44 injection.

    NOW... The Timbo APPS sensor... There is no set voltage tag because the switch for ON IDLE and THROTTLING is mechanical this means once the APPS sensor bellcrank gets to a particular angle THROTTLING starts regardless of voltage. So there is no voltage to adjust the APPS sensor to just a matter of taking the slack out of the APPS sensor bellcrank.

    So now you know why you DON'T set the APPS sensor for EXACTLY the tag voltage because now the APPS sensor idle validation switches will constantly flip back and forth between IDLING and THROTTLING causing issues with exhaust brakes, high idle software, etc.

    It's not about the voltage, it's about the fact of the APPS sensor Idle validation switch state...


    Problem #1 - Voltage on label

    Everyone is trying to hit APPS sensor voltage dead on what's on the tag... DON'T! This is the voltage that the APPS sensor goes from ON idle start to OFF idle state. Your voltage MUST be BELOW this number.


    Like on mine, the APPS sensor voltage is .519. Don't set the voltage at this set it below this mark say .480 to .490 because as you add in voltage gain or loss during normal operation of the truck it might cross the mark and go off idle and you end up with idle set at 950 to 1000. Then find out your exhaust brake, high idle and a few other things don't work!

    WARNING! STOP! Don't set the APPS sensor voltage to the voltage on the label this is WRONG!

    Like the Timbo APPS sensor, you adjust to the point you cross the dead zone and back off below this point 1/2 turn. The reason why is to keep the APPS from accidentally going to OFF idle state. As long as the voltage in the APPS sensor is below this state the ON idle signal is given to the ECM and the APPS signal is basically ignored and idle programming is used.


    Now if the alternator or voltage of the system changes a little bit you going to have issues of the voltage crossing back and forth over this boundary. Please set your voltage BELOW what on the tag by about 0.020 volts to ensure the voltage is low enough to put the APPS sensor in ON Idle state. If this was my truck to set I would set the voltage for .480 volts at the APPS sensor plug.

    Problem #2 - Where to measure the voltage?

    I do know why they started to measure the voltage at the PCM in concerns of the torque converter lockup problem, but this is wrong too. Now if you go over to my wiring diagrams here...

    And now look at Page 1 and look at the PCM on the right at pin #23 you see its labeled ACC PEDAL POS. You think this is tied to the APPS sensor?! Nope... Now switch back to page 3 now at look at the ECM on the right you find the wire at pin #28 on the ECM label ACC PEDAL POS SENS... But now look at all 3 pages this Orange/Blue wire doesn't connect to the APPS sensor at all, but it does pass the information to the PCM after it passes through the ECM (if there is any processing). So now look at Pin #25 on the ECM and you'll see it has a direct connection with the APPS. So if I was going to adjust the stock APPS sensor for voltage I would measure right at the APPS sensor or at the ECM pin #25 which happen to be light blue/black wire pin #3 on the APPS.

    WARNING! STOP! Don't measure the APPS sensor voltage at the PCM this is WRONG!

    Measure the APPS sensor voltage at the APPS sensor like Timbo does to if you're going for better measure it at the ECM. By the time you measure the voltage at the PCM there might be a minor voltage loss so the voltage at the ECM will be high so hence most people complain about high idle and other issues!


    The picture above is of Timbo's APPS sensor setup, but the wire color for a stock APPS sensor is Light Blue stripped black pin #3 of the stock APPS.

    The picture below is of the logic circuit within the stock OE APPS sensor and which you setting the voltage for not the PCM or ECM. This doesn't exist in the Timbo's APPS sensor.


    Problem #3 - How to adjust the APPS sensor?

    There is no need to yank the APPS sensor apart and mess with the 2 Torx screw on the back you can obtain all the adjustment you want in the set screw on the bellcrank. But once again don't adjust for the voltage marked on the label... Make sure to flick the APPS sensor bellcrank to WOT and let it snap back to idle a few times and check you voltage again if the voltage is changing constantly the APPS sensor is wore out and no amount of adjusting is going to fix this problem. Replacement of the APPS sensor is required.

    WARNING! STOP! Don't bother messing with the 2 Torx screw just adjust the set screw on the bellcrank.

    The problem with adjusting the APPS sensor by loosen the 2 Torx screw will now mess with the high side limit so since most of the time you are adjusting higher and find that now you can't get a full span of throttle you might come up to 5% short of WOT position. But if you just use the set screw on the bellcrank you won't effect the high side limit.

    Actually, once again there is no reason to adjust the APPS at the PCM... PCM has no bearing on the engine... The only thing the PCM wants to see is throttle position for an automatic transmission for shift point reasons and the PCM feed throttle information to the ECM for cruise control for later model Cummins. Still and all the ECM is more important to get the voltage value right.

    Problem #4 - Beware Of Out Dated Procedures

    After working with Timbo to understand and learning the differences of the Timbo APPS sensor and the OE APPS sensor. What I found out is that the voltage number on the label is the point at which the IVS (Idle validation Switches) toggle their position with reference to sensor ground. This why I'm warning about outdated procedures like the one over at CF.com .  Being that this article is highly used and wrong, it will produce a very poor adjustment of the APPS sensor. Why? Well, the procedure requires measuring the voltage all the way at the PCM. By the time the voltage is passed to the ECM and then back out to the PCM it's lower than APPS original signal which is typical so by the time you compensate for it now the voltage is too high for the APPS sensor and its stuck in throttling mode.

    Please don't use this proceed linked above it will cause problems for the APPS sensor!

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