Engine/Transmission (1998.5 - 2002) APPS reset - is this a typical finding?

[FTwardoch]

Did the 'real' APPS reset - remove the pump cover, check the voltage on the back of the APPS (. 535), probed the wire at the connector to the PCM... ..... and it read . 39V. Reset it to match the APPS but makes me wonder for those who've done this check/reset, have you found this much disparity?



Also, what changes should I see with the reset? Anything? Hoping it helps with my stacked shift issue (where the transmission goes from 3rd to Lockup/OD with no gap.

 

[Gary - K7GLD]

Did the 'real' APPS reset - remove the pump cover, check the voltage on the back of the APPS (. 535), probed the wire at the connector to the PCM... ..... and it read . 39V. Reset it to match the APPS but makes me wonder for those who've done this check/reset, have you found this much disparity?



Also, what changes should I see with the reset? Anything? Hoping it helps with my stacked shift issue (where the transmission goes from 3rd to Lockup/OD with no gap.

SO, what changes in driving characteristics have YOU observed from your recalibration?

 

[mhenon]

Did the 'real' APPS reset - remove the pump cover, check the voltage on the back of the APPS (. 535), probed the wire at the connector to the PCM... ..... and it read . 39V. Reset it to match the APPS but makes me wonder for those who've done this check/reset, have you found this much disparity?



Also, what changes should I see with the reset? Anything? Hoping it helps with my stacked shift issue (where the transmission goes from 3rd to Lockup/OD with no gap.

Exactly how did you "reset" the voltage on the PCM connector?

Mike

 

[FTwardoch]

Exactly how did you "reset" the voltage on the PCM connector?

Mike

It's not on the PCM connector. You first measure the voltage AT THE PCM (closest plug grouping to the engine) on the orange wire w/blue stripe with key on. It measured . 39V. Then you remove the cover over the APPS, remove the six 10mm bolts holding the array on, read the back of the APPS for what voltage it 'should' be, then if the voltage doesn't match what you read off the PCM wire, you loosen the two Torx-20 bolts on the back of the APPS, turn either clockwise or counterclockwise while consulting your voltmeter. When the voltage matches what it should be, tighten down the T-20 bolts and button it all back up.



As far as driving impressions, I haven't gone far enough to say for sure, but it does not appear to shift up as soon going from 3rd... ... ..... tomorrow going to work on the freeway will tell.

 

[ARoss]

Been there, done that! It makes a difference for a while, but, ultimately, you'll have to change the unit. I set mine several times to buy some time. It gets to be a PITA after a while, so the Ebay alternative supplied me with a new unit for a couple of hundred dollars ... much easier on the mind and the wallet!

 

[Fishin Guide]

The APPS calibration just matches the calibrated value on the APPS to what the PCM should be seeing at idle.



Now, by raising or lowering the voltage, you take active control over lockup. Lockup happens at a specific voltage. Want sooner lockup? Raise the voltage.



You issue sounds more like a cable adjustment than anything else. Is there any free travel on the trans end when the pedal is at WOT?



Dave

 

[Gary - K7GLD]

I appreciate the info this thread provided - was always curious as to the observable effect the recalibration might provide - thanks.





For those interested, here's the calibration procedure from an earlier thread:







RESETTING THE APPS SENSOR.

(ACCELERATOR PEDAL POSITION SENSOR)

2ND GENERATION 24 VALVE TRUCKS ONLY.



LIST OF TOOLS NEEDED



DIGITAL VOLT METER

# 20 TORQUE BIT SOCKET

# 1 PHILLIPS

# 10 MM SOCKET



Proper service and repair procedures are vital to ensure personal safety of those performing the repairs. Standard safety procedures and precautions should be followed at all times to eliminate the personal injury or improper service, which could damage the vehicle or compromise its safety.

Although this material has been prepared with the intent to provide reliable information, no liability is assumed in reliance of this material.



It has come to my attention that a lot of people think by disconnecting & re-connecting the batteries and stepping on the throttle it is going to reset the apps, no, that is not correct. It is impossible to adjust your apps if you do not know where it is supposed to be set at. That is why you need the voltmeter.



This is the procedure I use to re-set the apps.



With the key on, engine off you need to probe the apps wire to see where your voltage is currently set at.

The best location to probe the wire is on the PCM (power control module) which is located off the passenger side of the firewall.



· You want the C1 connector, this is the connector closest to the engine,

· You want the orange wire with the dark blue tracer which is pin # 23

· Voltage should read somewhere around 0. 5 volts,

· At this point the voltage reading does not matter, it just has to be accurately written down for later reference.



*** TURN THE IGNITION OFF ON THE TRUCK ***



· The apps sensor is located slightly above and a little to the left of the injection pump.



· Remove the black plastic cover that is located by your injection pump.



The two screws that are holding it are plastic, do not put any downward pressure on them or you will never get them off.

· Un do the 6 - 10 mm headed bolts that hold the bracketry in place.

(DO NOT REMOVE THE CABLES)



You will notice the apps is on the back of the bracketry that you just removed, it is held in place by 2 - 20 bit screws. These screws have a little bit of locktite on them so make sure you have a good socket and gently give a little tap with a hammer before attempting to loosen. Be very careful these screws strip very easily and you only get one shot at them.



· On the apps you will find a white tag that gives you the information on what the apps adjustment should be.



· After loosening the screws you can rotate the apps both clockwise and counter clockwise to get the adjustment you need.



· The reading you took at the beginning of the process on pin # 23 should match the white tag on your apps, if not adjust accordingly.

 

[FTwardoch]

OK, first freeway run since the APPS adjustment - the 'stacked shift' issue is clearly better. No question.



I'll check my transmission 'kickdown' cable next just for clarification purposes. I've read the adjustment threads so that will be next.



"One adjustment at a time". Good mantra.

 

[mhenon]

OK. . so this APPS adjustment is for automatic's only... ... ... ... ... ... ... right?

I don't want to sound tooo dumb here but this is the first I've heard about this procedure.

Mike

 

[Gary - K7GLD]

OK. . so this APPS adjustment is for automatic's only... ... ... ... ... ... ... right?

I don't want to sound tooo dumb here but this is the first I've heard about this procedure.

Mike

No, the stick engines also use the APPS.

 

[PC12Driver]

No, the stick engines also use the APPS.

Half right. Of course autos and manuals both use the APPS for throttle info since our engines are "drive by wire" (no mechanical linkage between the throttle pedal and the injector pump). But only the auto needs to have the APPS reclocked to match voltages with the PCM (the procedure pasted above). That way the PCM knows what the throttle position is and can shift/lock up accordingly. On a manual truck the APPS signal provided to the PCM is useless, so reclocking the APPS to match the voltage is a waste of time.



Here's a previous discussion on the whole APPS "calibration" thing.

 

[mhenon]

No, the stick engines also use the APPS.

THE SIX SPEEDS HAVE AN APPS??????????.

Really... I've never heard of this adjustment before this thread.

So is this something you just check once in awhile... once a year... when you're having engine problems or what?

I've done the key on, pedal down thing after pulling the batteries. . but this is a new one for me.

Mike

 

[mhenon]

Half right. Of course autos and manuals both use the APPS for throttle info since our engines are "drive by wire" (no mechanical linkage between the throttle pedal and the injector pump). But only the auto needs to have the APPS reclocked to match voltages with the PCM (the procedure pasted above). That way the PCM knows what the throttle position is and can shift/lock up accordingly. On a manual truck the APPS signal provided to the PCM is useless, so reclocking the APPS to match the voltage is a waste of time.



Here's a previous discussion on the whole APPS "calibration" thing.

OK... you posted while I was typing. That clears it up.

Mike

 

[Gary - K7GLD]

PC12Driver]Half right. Of course autos and manuals both use the APPS for throttle info since our engines are "drive by wire" (no mechanical linkage between the throttle pedal and the injector pump). But only the auto needs to have the APPS reclocked to match voltages with the PCM (the procedure pasted above). That way the PCM knows what the throttle position is and can shift/lock up accordingly. On a manual truck the APPS signal provided to the PCM is useless, so reclocking the APPS to match the voltage is a waste of time.

HMMMmmm - that's interesting - I can see where the APPS setting would be MORE critical for the AT's - but have never heard it was a "waste of time" to maintain calibration on the manual transmission trucks...

 

[PC12Driver]

The ECM will learn the minimum and maximum voltages from the APPS and will use these values as idle and full throttle. Or you can disconnect/reconnect the batteries and run the pedal through full travel to help it along. So, as far as engine control, any variations in the APPS voltages will be taken care of automatically.



The PCM (shifting), however, doesn't self calibrate. That's why you need to match the voltages on the tag with the actual APPS output by re-clocking the APPS potentiometer (the method you listed). Then the PCM (shifting) and the ECM (throttle) are on the same page as far as proper gear/lockup versus pedal position (engine load). And after the APPS is reset to match the PCM's required voltage at idle, then the ECM will automatically adjust to the new voltages.



Since the PCM in a manual transmission truck does absolutely nothing with the throttle position info, there isn't much reason to adjust the APPS. Thus, a waste of time.

 

[alonzo]

apps/6 speed

Since the PCM in a manual transmission truck does absolutely nothing with the throttle position info, there isn't much reason to adjust the APPS. Thus, a waste of time.

My `01 truck with 6-speed, after some time of highway running (trailer or no trailer) occasionally idles at around 1100 rpm until I shutdown/restart. Dealer said it was the APPS dissagreeing with the ECM (or some such). I've not tried any 'reset' or 'recalabration' on it. It's done this for so long that I don't remember when it started (now at 67000 miles). Idle goes back to around 850 rpm after a restart. Dealer wants around $500 to replace the APPS but it doesn't bother me that much!