2003 dodge ram 1500 P2138 flashing lightning bolt

Justin Owner Massachusetts Posted   Latest  
Resolved
Driveability
2003 Dodge Ram 1500 Laramie 5.7L (D) 4-spd (46RE)
P2138 — Throttle/Pedal Position Sensor/Switch "D"/"E" Voltage Correlation
Limp Mood
Flashing Lighting Bolt

I've done resistance testing on all 6 wires from apps to PCM this is the apps system under the battery tray. a new apps is nonexistent closets thing I can find is a TH456 made by standard and its 400+ But all the information on it says will not work on a 1500 5.7 I'm not sure if this is true or not. New ETC and did a relearn multiple times. I do not have a lab scoop but in live data on my scan tool, I can see apps signal voltage drop to zero every 5 seconds or so and this happens while key on engine off or key on engine on. Both apps signal 1 and 2 both raise and fall smoothly when depressing and releasing the accelerator pedal and compared to other waveforms seems to be normal with the exception of this intermittent voltage drop over a period of milliseconds every 5 seconds or so others no apparent pattern to the voltage drops. The truck was given to me as the customer has had enough of it and at this point just trying to get some money back if possible. last year he put a PCM in it by someone else and worked for a while then an ETC which I put in and worked for a while now Im down to this nonexistent. also the apps sensor I've removed has a Mercedes logo on it which makes sense as I believe Chrysler and Mercedes were together at that point. I guess my question is anyone have a line on a cheaper alternative for the apps sensor or am I missing anything because I see a lot of talk that replacing the app's sensor did not fix this issue for many. also the smooth operation of both sensors leads me to belive it may not be the apps I also rigged up a bench test with a 5 volt supply ground and voltmeter and both signal wires and grounds all worked and readings raised and fell smoothly. 

0
Interesting
Dan Owner/Technician
Texas
Dan
   

… Resistance tests are not good enough…isolate these circuits on BOTH ends and try to power a sealed beam bulb thru them one at a time… bright burn = good circuit wire… dim (or non burning) bulb = bad circuit wire… Dan H. …Hobbs … South Texas …

+3
Ð Awarded
Agree
Helpful
Justin Owner
Massachusetts
Justin
 

I like that ill give it whirl and should be quick as I think Ive memorized each pin and color code over the past few days. although I might justify this as my excuse to buy a picoscope.

0
Ð Awarded
Oscar Mechanic
California
Oscar
 

The after market staff specially electronics do not work in Dodge very well need Mopar parts and disconnect battery touch positive and ground together for two minutes to clear memory and start all over.

0
Ð Awarded
Jesse Engineer
Missouri
Jesse
 

Had a similar issue with a 2010 Charger. It'd drive fine, then randomly fall on its face with the same issues you have. Replaced throttle body with a used one. Was better for a couple of days then started again. Replaced throttle pedal with another usex one and it fixed it. The computer monitors all 3 circuits simutanilously. Overly redundant for safety. If there's any hickup in any one of the…

+1
Ð Awarded
Justin Owner
Massachusetts
Justin
 

I cant lie I played around with a few jumper wires from the apps back probed into the pcm with no difference. I even gave the signal wire a bump of my own voltage from 1-3 volts while scan tool was on I could see the volts and still this intermittent voltage drop. i jumped signal, ground and the 5volt directly from the pcm to no avail all showed this voltage drop.

0
Ð Awarded
Glenn Owner/Technician
Texas
Glenn
 

Hi Justin, You need a scope, even a small pocket scope, to catch these kinds of issues, a scanner has too much lag/refresh time. Dan is making the same suggestion I would, the wires need to be isolated and load tested with a power source and a halogen bulb. That is a proven method that has worked for many years before scope became common. First came a code, next came a part, next came back up…

+5
Ð Awarded
Agree
Justin Owner
Massachusetts
Justin
 

yup Im wanting and loo… into a scope weather it helps this truck or not and Im by far a tech but I certainly try to be. yes using Mitchell followed flow charts, even picked off some flow charts that I thought would be related that I don't have codes for. so as of right now the only issue I had with the flow charts was scoping apps signals 1 and 2 and was attempting to make up for it using the…

0
Ð Awarded
Matt Technician
Texas
Matt
 

Get the u-scope from AES Wave, they have a nice kit for cheap, that way you can get started working with a scope and later upgrade for a bigger one. Plus it is really handy to have, even if you have a pico it is nice to have a small one for quick testing.

+3
Ð Awarded
Agree
Justin Owner
Massachusetts
Justin
 

going to look right now. im never afraid to spend the money I don't have on new tools. sometimes they make up for the technician Im not.

0
Ð Awarded
Glenn Owner/Technician
Texas
Glenn
 

Hi Matt and Justin, Autel also makes a decent scope kit. It is similar to a Hantek and it is a 4 channel which is common these days. PICO is nice, but they are pricy. Has you get proficient with scopes, maybe a PICO will soon be justified.

+1
Ð Awarded
Sherman Owner
Texas
Sherman
 

Glenn, I've found that mu Autel 4 channel is quite user UNfriendly! It makes me feel dumb as a rock.

+1
Ð Awarded
Justin Owner
Massachusetts
Justin
 

shoot I'm sad to hear that I like autel tools and was loo… at their scope, what do you find unfriendly about it?

0
Ð Awarded
Glenn Owner/Technician
Texas
Glenn
 

Hi Sherman, I am not a daily or power user of scopes, but they are necessary with todays electronics. They take plenty of practice. The Autel does not have the auto presets like PICO. I typically start with my setting higher than the system being tested, then set a longer time base for the data capture. From there, it is a matter of dialing in the settings. Autel and Hantek are both good basic…

0
Ð Awarded
Phillip Educator
Ontario
Phillip
 

A dropout on one of the APP signals every few seconds is probably normal and is a designed glitch built into the sensor circuitry to ensure its a real signal and not a stray voltage from another circuit. When graphing the signal on a scan tool the signal may appear to randomly drop out due to the refresh of the data. This is common on Chrysler and GM APP sensors. I agree with the other guys lold…

+1
Ð Awarded
Justin Owner
Massachusetts
Justin
 

certainly doing this in the morning. I'll even be one of the few that'll post where I end up. I can't complain I've been playing mechanic/tech for 20 years off and on and I think this is going to be the first one Im going to loose my shirt over. So Im sort of determined to at least get a learning experience out of it. My first mistake was assuming I could find a part that is discontinued my…

0
Ð Awarded
Dwight Owner/Technician
California
Dwight
 

Agree on the dropout. I believe it's PCM check of the circuit.

0
Ð Awarded
Robert Technician
Michigan
Robert
 

Fact or Fiction Bosch a… works but its 's dirt cheap used on a boat load of late 90's early 2000 Mercedes models…How did you arrive at the Standard 456 a Mercedes Benz part # but has a different 6 pin connector than MOPAR??? You wont find that Dodge RAM part that 2003 is year specific the only year RAM 5.7 that used the Benz set up of the throttle cable to the APPS

0
Ð Awarded
Justin Owner
Massachusetts
Justin
   

I came across the Th456 searching dodge bellcrank. yes the one I have is a 6 pin one row and I have come accross that bosch number multiple times but that too seems to be 2 rows of 3 pin connectors. today im going to load test the wiring because late last night I did see in a service manual my voltage drop is normal. amongst a few people here saying it was normal so further diagnoses into the…

0
Ð Awarded
Raymond Mobile Technician
Michigan
Raymond
 

hi Justin, I agree with Phillip, it is normal for APP to glitch as it does a self check, when it comes to Chrysler products I will tell u it is dealership or nothing. Aftermarket parts can't make them to OEM specs. I have experienced this many times and Chrysler is the worst for requiring OEM parts, sometimes it worth a 50/50 shot to get a used part from a salvage yard over aftermarket, u mite…

+2
Ð Awarded
Justin Owner
Massachusetts
Justin
 

Yes I too agree with you Dwight and Phillip the voltage drop is normal as I found it said so in a service manual. So today we going to take a good hard look at the wiring…for the 4th time this time with a load.

+1
Ð Awarded
Thanks
Justin Owner
Massachusetts
Justin Update
 

So I load tested all 6 wires from apps to pcm with a 55w headlight bulb. Did quick resistance test on each wire first to be sure I was on the right one grounded on the pcm side and put my “test light” on the apps side. Bright as day on all 6 wires. Next I'll do the same to the 6 wires on the ETC I also noticed I got .9 amp parasitic draw so for shitz and giggles hooked up an Amp meter and…

0
Update Ð Awarded
Harm Technician
Ontario
Harm
 

i would check the 5 volt supply for something that interupts the driver in the pcm. had a few fuel tank pressure sensors shorting down the 5 volt supply down to 4.8V and not set any other codes except the app1 and 2.

+2
Ð Awarded
Agree
Justin Owner
Massachusetts
Justin Update
 

So today found the transmission module is pulling 70 milliamps key off doors closed and locked and asleep. guess it's back to the wiring diagram.

0
Update Ð Awarded
Justin Owner
Massachusetts
Justin Update
 

Well I said Id update and here it is. after finding out the pcm was replaced so was the tcm by someone else. apps sensor appeared to be functioning normally and the rats nest found under the intake scrap yard is on its way and giving me 800 for it. I got me money back and a couple hundred and 1 miserably failed repair attempt for me. oh well cant win them all

0
Update Ð Awarded
Justin Owner
Massachusetts
Justin Resolution
 

1 to the yard and 1 failed mission on me.

0
Resolution Ð Awarded