Slow/dead pedal at startup

[ewo1]

So I have found in dealing with international components, that for a drive by wire pedal replacement you MUST sync the replacement pedal to the PCM. You need to have the PCM 'learn' the new idle and WOT points of the pedal basically , if not the pcm will not recognize the new hardware.

Hi there poppa,
Not to challenge you in any way, shape or form but I read it differently… from the tech doc I uploaded in post #17.

The doc ( page 3) says that the APS auto learns each and every time you turn the key switch on.

I ordered a new TPS sensor today from an outfit in Florida, $60 bucks.
I hope it works !
Stealer wanted $380 for the sensor and $800 for the pedal assembly!


EDIT:

After re-reading your post, your right...but I guess it's done automatically ???

 

[Kentucky Dreaming]

I ordered a new TPS sensor today from an outfit in Florida, $60 bucks.
I hope it works !
Stealer wanted $380 for the sensor and $800 for the pedal assembly!

 

[LargeMarge-TC]

So I got an interesting issue going on my 2nd bus...

.
I saw your '2nd', and my tiny brains read it as 'tuned'.
Weird, eh?

 

[ewo1]

.
I saw your '2nd', and my tiny brains read it as 'tuned'.
Weird, eh?

?????What do you mean???

Too much fun in the sun...??

 

[ewo1]

So I have found in dealing with international components, that for a drive by wire pedal replacement you MUST sync the replacement pedal to the PCM. You need to have the PCM 'learn' the new idle and WOT points of the pedal basically , if not the pcm will not recognize the new hardware.

Hey there Poppasmurf,

I was really curious to better understand what you were trying to share regarding the "Learning" the new idle and throttle points.

While doing some deep google research I found an old thread here where this was discussed and I gotta give it to you, you were right on the money.

Here is the old thread -> https://www.skoolie.net/forums/f13/gas-pedal-error-code-****-help-26337.html.

I got my new sensor, I ordered a 400467 sensor from Advanced truck parts in Sunrise Fl.
Why that number???

My "9906" bus ('99 Amtran), the part number on the pedal sensor was 400468 and the best that I could find/figure out was that the 400467 was a replacement for the 400468.

The 400468 appears to be an OEM number and is also the sensor that is put on the DORMAN pedal assemblies.

Well I wasn't gonna pay $250 bucks so I went with the 400467 for $60 bucks.

When I put the new sensor (400467) on my '05 Amtran, it worked but it was not really responsive, felt like the RPM's went up slowly. Bus moved though!

Then I switched pedals again, put the old 400468 on the '05 bus and the new sensor, 400467, on the '99 bus and now both units have responsive pedals.

I'm now thinking it might be because of the different flash's on the ECM, throttle response curve recognition???
Both sensors have different resistive values???

Maybe that's why when I did my initial testing one bus I got the "Warn Engine" light on one bus but not on the other, because of the different flashes?

So the part number on the bad sensor, turns out that it is 132617, which you can get real cheap at Advanced truck parts.

I'm gonna go ahead and order the 132617 and put it back on the '05 bus just to see what it does. It's worth the $30 bucks or so to find out!

Caddilackid, you also were on that thread too with real good info on the subject matter!
You said "this is a great thread for those that need to replace those pedals.." and I have to agree with you, it explains it in real plain english!

:marshmallow:

 

[ewo1]

So I am finding some more "intermittent" dead pedal issues... I have decided to revive this thread and add more info so others down the road can have a reference source...

I haven't driven the Milkshake bus all year (2024) other than to do short 5 mile rides just to keep her charged up and lubed...DT466e's I understand don't like sitting and not running for long periods of time....

I finally decided to work on the Hard Start-long crank situation that I never got resolved last winter (2023), those results are for another thread, but what I did experience was a total loss of pedal while sitting and running several auto tests in Servicemaxx.

Initially I was looking at and verifying the Accelerator Position Sensor/Idle Validation Switch - APS / IVS in service maxx and everything was looking and working just fine. Minutes later while doing other test I got DTC 135 & 134.

134*† 91 0 7 APS/IVS (page 300) APS signal and IVS disagree
135*† 0 230 11 APS/IVS (page 300) Idle Validation Switch circuit fault
After turning the key off and back on, pedal works again. Drove it for 35 miles, mostly highway, no issues.

This is what the manual, EGES-270-1 has to say about it...

Fault Detection / Management
When the key is on, the ECM continuously monitors the APS/IVS circuits for expected voltages. It also compares the APS and IVS signals for conflict. If the signals are not what the ECM expects to see, Diagnostic Trouble Codes (DTCs) will be set. Any detected malfunction of the APS/IVS sensor circuit will illuminate the amber ENGINE lamp. If the ECM detects an APS signal Out of Range HIGH or LOW, the engine will ignore the APS signal and operate at low idle. If a disagreement in the state of IVS and APS is detected by the ECM and the ECM determines that it is an IVS fault, the ECM will only allow a maximum of 50% APS to be commanded. If the ECM cannot discern if it is an APS or IVS fault, the engine will be allowed to operate at low idle only.
That last sentence has me stuck... My amber light did not come on when the issue occurred, dead pedal-YES!

I drove it from TX to Miami and back last year after I had replaced the pedal sensor, no travel issues!
I am not too concerned at this point about getting stuck/broke down with a dead pedal because a simple turn of the key switch will clear the codes but I would like to know why this is happening.

Here is what else the service manual has to say...

DTC 134
APS signal and IVS disagree

• If neither the APS or IVS is changing, or both are changing, or the ECM cannot determine the DTC in specified time, DTC 134 is set and engine rpm is restricted to idle.
• When DTC 134 is active the amber ENGINE lamp is illuminated. (mine did not illuminate)

DTC 135
IVS circuit fault

• If the APS is changing but IVS is constant, the ECM assumes the IVS is the conflict source and sets DTC 135. In this case the ECM limits the APS signal to a lower value that provides less than full rpm, but does not limit engine rpm to idle.
• When DTC 135 is active the amber ENGINE lamp is illuminated.

DTC 133, 134, and 135 are caused by intermittent conditions. These DTCs remain active until the vehicle has been shutdown and restarted. They do not recover without cycling the ignition switch. Later calibration versions may allow DTC recovery without cycling the ignition switch.

Note: replacing the APS/IVS doesn't not require ECM calibration as every time you turn the key switch on it auto self calibrates.

Anybody got any ideas or thoughts on why/how this could occur?

Caddilackid...where for art thou ???

 

[Jolly Roger bus 223]

have you been using manufacturer parts?
i replaced a throttle position sensor in pedal with Dorman on a truck that might move on the weekends and had issues opened it up and it had moisture in it from temperature change i guess?
so unit wasnt sealed but then again sealed might have been worse.
and i have been wandering a caddilac kid as well.

 

[ewo1]

No, I am not using OEM.
Going OEM cost too much for a simple sensor. Stealer, and Dorman will only sell it with the pedal assembly. Don't need/want a new pedal assembly.
$250 vs $60...If was an IPR or other engine sensor I would spend the money without hesitation.

The moisture issue I don't think is it for me. Interesting point though!

I read somewhere that the VCC for the pedal sensor is shared with another sensor. I'm gonna look at that just see what is going on but otherwise, I am stumped !

 

[ewo1]

Ok, just took a look at the wiring diagram and it appears that the BAP shares VREF (+5v) and Ground with the APS/IVS. Gonna look at that tomorrow....

 

[Mr P]

Fly by wire is a wire pulled throttle, (manual).

NO, that is backward. "Fly by wire" is electronically controlled via wires.

Comparing sensor values with a "scanner" will probably reveal which data is erroneous or show if the 5v reference circuit is failing.

 

[ewo1]

NO, that is backward. "Fly by wire" is electronically controlled via wires.

Comparing sensor values with a "scanner" will probably reveal which data is erroneous or show if the 5v reference circuit is failing.

Mind sharing what scanner to use for testing BAP sensor...beside o-scope or multimeter.... I have both...

Beside resistance and voltage checks, what other testing can be done to the BAP sensor?
And If I were to use the o-scope, what kind of waveforms should I expect to see and under what test conditions?

I've taken approx 5 local drives so far, 200+ miles, 0-70 mph both city and highway and the issue does not occur while driving.
If I let it sit and idle for more than 20 minutes, that's when I can expect to find the dead pedal. Restart and she runs fine....

 

[Mr P]

I'm only a light truck/passenger car mechanic. Little stuff like that uses the OBDII connector, and I use a snap on scanner with lab scope. I can't give you the advice you seek, sorry.

IF your code is for a "mismatch" of pedal and injection command, I would graph/scope both sensors if possible. When the code sets the graph/scope should tell you a lot.

 

[ewo1]

I'm only a light truck/passenger car mechanic. Little stuff like that uses the OBDII connector, and I use a snap on scanner with lab scope. I can't give you the advice you seek, sorry.

IF your code is for a "mismatch" of pedal and injection command, I would graph/scope both sensors if possible. When the code sets the graph/scope should tell you a lot.

The problem I see with trying to use an o-scope, and I know how to use one, is that the bap is designed to respond to certain environmental conditions, one of them being altitude.
Would I have to reproduce theses environmental condition to test the BAP?

The APS/IVS would be rather easy to test on an o-scope. this part is super easy.
One half is nothing but a potentiometer and the other half is nothing but a simple hall effect sensor.
The only variable I see that that might be an unknown would be the resistance value of the potentiometer...
What I mean is that I do not know the OEM resistance value but in all reality its a non issue as in the end it's nothing but ohms law.
for instance, if the OEM resistance value is say 100 ohms and the one I replace it with is within let's say, a 10% differential then the pedal should be just fine.
But if the resistance value was say, 100's or thousands of Ohms off target then the pedal would not work properly.

The hall effect sensor is nothing but an on/off switch.

I really do not see a way to use an o-scope on the BAP...without a reference chart, a waveform chart to compare with the actual reading, it would be impossible to know/interpret the o-scope wave form.

Yes, I could probably see some amplitude and maybe see voltage changes, but what about frequency?
Are there any specs out there that would indicate frequency responses? What would we use as a baseline for referencing?

I guess I could o-scope the power wires and look for "Noise" on the voltage line...that might get me somewhere...but where?

Interesting question just came to mind while writing this....can noise, and how much noise, affect the ECU?

where would noise come from, alternator ???

Just for chit and giggles I think I gonna check for noise, just to see if it is even there?

 

[nikitis]

You'd probably have to put the bus up in the air in the rear end, so the wheels can spin without the bus moving. Get your reference from using your pedals while working, then when it fails measure it and compare it again.

 

[ewo1]

You'd probably have to put the bus up in the air in the rear end, so the wheels can spin without the bus moving. Get your reference from using your pedals while working, then when it fails measure it and compare it again.

I can see APS/IVS movement in Servicemaxx, that not a problem... It's the BAP and the side effects on the circuitry that BAP issues could/might present. Lifting in the air and free wheeling the tires is not gonna help.

Me thinks a load, engine/tranny, needs to be present in order to electronically view the BAP system as if we were reproducing real life driving..
Otherwise all measurement would be static and not truly representing life driving situations. I could be wrong but that's how I see it so far...but honestly,

I am just wildly fishing right now with ideas on how to address a potential test.
I know there are steps for voltage and resistance measurements/testing the BAP. I was just thinking outside the box on this to better understand what is going on.

 

[skoontz]

I had a similar issue when I purchased my bus. I don't remember exactly what codes it threw, but yours sound familiar. The symptoms certainly do. I'd be driving along, and then the check engine light came on and the engine would only idle. But it was an intermittent problem. My mechanic even put the bus on jack stands and ran it to try to have the issue pop up (which of course it didn't). Turns out there was a issue with the wiring going from the gas pedal to the ECM where one of the wires was making intermittent contact. He ended up replacing the wiring going from the pedal to the ECM, and I haven't had the problem again. Not sure if a wire was broken or if it was a corrosion issue. Good luck!

 

[nikitis]

I can see APS/IVS movement in Servicemaxx, that not a problem... It's the BAP and the side effects on the circuitry that BAP issues could/might present. Lifting in the air and free wheeling the tires is not gonna help.

Me thinks a load, engine/tranny, needs to be present in order to electronically view the BAP system as if we were reproducing real life driving..
Otherwise all measurement would be static and not truly representing life driving situations. I could be wrong but that's how I see it so far...but honestly,

I am just wildly fishing right now with ideas on how to address a potential test.
I know there are steps for voltage and resistance measurements/testing the BAP. I was just thinking outside the box on this to better understand what is going on.

But lifting in the are with tires spinning does recreate driving conditions as far as the engine is concerned. It's not measuring loads, only monitoring RPM and Throttle values and shifting based on wheel spin. The bus won't know it's not really driving.

 

[ewo1]

But lifting in the are with tires spinning does recreate driving conditions as far as the engine is concerned. It's not measuring loads, only monitoring RPM and Throttle values and shifting based on wheel spin. The bus won't know it's not really driving.

This is true but engines do respond differently under loads that not under a load. This cannot be disputed but again, you are still correct with your explanation.
For simple testing, yes. for complex testing, you need a load...

 

[nikitis]

Well you can see if it works with a simple test of lifting it up in the air and probing it while fake driving and see if it fails

 

[Mr P]

What is a BAP and how does it relate to your codes that indicate problems with the APS/IVS?

Googling for 10 seconds showed me that a BAP was the baro pressure sensor. I'm going to SPECULATE based on the t444e/7.3 engines that I've worked on, that the BAP has nothing to do with those sensors, UNLESS they share a power or ground wire. The BAP will only change "with the weather".

Your codes indicate a mismatch between the APS and IVS. The computer is going to "expect" a certain APS when the IVS indicates idle position. Isn't the IVS an on/off switch at idle? Doesn't the APS produce a couple of comparable voltages....

CAUTION: Car info follows: some cars have one sensor that ranges from 0 to 5 volts while the other ranges from 5 to 0, they will always "mirror" each other with a voltage that totals 5 volts. If the computer ever sees a total that is NOT 5 volts, it has no idea where your foot is and gives you idle speed.

So how does your bus APS work? I speculate you will have two variable voltages from idle to WOT, and one IVS that switches as the pedal moves from the rest position.