[KevinsOffroad]

If that is the power wire from the ECM and it shows 5.01v, the wire and ECM should be fine. Pin 3 should sow .5v at idle key on or running. It should smoothly graduate to about 3.8v at WOT.

Ok, I'm getting a smooth transition from 0.48v. on pin 3 to 3.68v. at WOT, so sounds like we're good there!

 

[KevinsOffroad]

What band apps is on it now, Factory, Timbo(it has a 3" pigtail).

Looks to be a factory Mopar, p/n 56028184AB 9323RF 0.613 VDC

 

[KevinsOffroad]

...Then I got to Step 3, which is "Turn ignition off. Ensure APPS harness connector is still disconnected. Check for continuity between terminal No. 4 (Black/Yellow wire) and terminal No. 5 (Dark Blue/White wire) on APPS harness connector. If continuity does not exist, go to next step. If continuity exists, repair short between Dark Blue/White and Black/Yellow wires. The Black/Yellow wire is the sensor ground circuit."

I AM getting continuity between those two wires...so looks like there may well be a short.

My question is this: IS THERE A TYPICAL LOCATION I CAN BEGIN LOOKING THAT THIS SHORT FREQUENTLY OCCURS?

I figure I'd ask the question here, since a bunch of you guys have had this issue, and I'm sure have located where the short was...rather than me just blindly ripping apart wiring harnesses randomly.

Just an update on this. I'm getting 1770 ohms between T4 and T5 on the APPS harness. According to MoparMan's writeup as quoted above, I should be looking for a short between those two wires...both coming from the ECM (T31 and T32) unless 1770-ohms is "normal"...?

 

[KevinsOffroad]

Just an update on this. I'm getting 1770 ohms between T4 and T5 on the APPS harness. According to MoparMan's writeup as quoted above, I should be looking for a short between those two wires...both coming from the ECM (T31 and T32) unless 1770-ohms is "normal"...?

Pulled the ECM harness off the ECM, and found a bunch of dust/dirt. Cleaned it with a clean rag first, then with CRC Lectraclean on the ECM side and the harness side.

That 1770 ohms I was getting between T5 and T4 on the APPS harness when it's plugged into the APPS, which goes UP to 2560 ohms when I disconnect the ECM harness from the ECM!! Literally, as I connect and disconnect the ECM harness from the ECM, the ohms increase and decrease.

When I disconnect the APPS harness from the APPS, I am able to replicate the same issue, via the wiring harness, pins 4 and 5, but the ohm reading is around 1550 ohms.

I've replicated this test three times now, same numbers.

Any ideas here?

 

[KevinsOffroad]

Another datapoint:

I tested continutity between T4 on the APPS harness to T32 on the ECM...and it was a closed circuit
I tested continuity between T5 on the APPS harness to T31 on the ECM...and it was a closed circuit
I tested for a short between those two wires (DB/WH and BL/YL) wires at the APPS harness (T4 and 5) and then again at the ECM harness (T31 and 32) and did NOT get any cross-continuity...open circuits, both of them.

So...I'm REALLY glad I didn't tear into my harness looking for rubbed wires...when both ECM and APPS connectors are unplugged, I'm not getting ANY indication of a short between those two wires.

Current working theory: I either have a partial short inside the ECM causing the continuity reading (per step 3 above), or...I don't know...that seems like the only explanation at this point. The APPS itself SEEMS to be giving us the correct readings.

Thoughts?

 

[KevinsOffroad]

Actions Taken:
Ran an 8-ga., 1-foot long experimental "ground tap" from terminal 4 (BK/YL) on the APPS harness directly to the engine block (top/forwardmost bolt ((1 of 6))) of the throttle "bell-crank" assembly. I'll report my findings.

Ordered up the Wells/ WVE 5S5352 sensor from RockAuto to have a spare one on board. When it comes in, I'll swap out my Mopar one and see if that makes any difference at all.

Concern:
Seems like I have an internal short inside the ECM...maybe? If that's the case...what's my next step?

Thank you guys for all your help!!!!

 

[afterburn549]

Beyound my skill set. If you are satisfied all is grounded well, and the WTS light works ...IDK
If you do send off your ECM, only send to the recommended shops.

 

[KevinsOffroad]

Beyound my skill set. If you are satisfied all is grounded well, and the WTS light works ...IDK
If you do send off your ECM, only send to the recommended shops.

Wait to start light appears to be working just fine. When I wait the 2-15 seconds it asks me to, the engine consistently fires right up nearly immediately.

 

[afterburn549]

Not in my wheel house.

 

[bigfish95971]

You seem to understand all this. Have you read/done this?

P0122 APPS Sensor Signal Voltage Too Low

DTC P0122: APP SENSOR SIGNAL VOLTAGE TOO LOW Monitor & Set Conditions Accelerator Pedal Position Sensor (APPS) voltage is monitored when the engine is running. DTC may be stored if low voltage is detected on APPS signal circuit or low voltage is detected between Engine Control Module (ECM) an...

mopar1973man.com

 

[KevinsOffroad]

Ok, taking the next step involved me getting a hold of AutoComputer Specialists in Florida, per MoparMan's guide here:

List of Verified and Reliable PCM/ECM Rebuilders

Hey Guys, <<For a List of vendors who have supplied junk parts or didn't stand behind their products....see the bottom of the article.>> pepsi71ocean here. I decided to finally write this article up after another round of people with issues with reman companies. So a while ago back in...

mopar1973man.com

Just got off the phone with Demetrius, who was very helpful. He says that the APPS low voltage P0122 code is EXTREMELY common with an ECU that's going out, (as is the Wait to Start light issues, as mentioned above)

They offer a $228 service to repair mine, or $588 for a swap with a refurbished one (+ a $500 core charge). They offer an $88 "RUSH SERVICE" which equates to a same-day repair...else it's 2-3 day turn-around without the RUSH.

He also said that due to the physical location of the ECM...with all the heat and the vibration, that they typically only last 200k-250k before they need to be repaired or rebuilt. I have 210k on mine...so I'm right in that range. I think mine is probably OE, because there's a "VOID" sticker between the harness and connector that appeared to be fully intact when I removed the ECM harness from it earlier today.

I'm thinking I'm going to pull it and overnight it, due to what I'm seeing from my testing. Worst case is the ECM is NOT the problem and I spent a few hundred bucks I didn't NEED to...but I get a tested/repaired ECM out of the deal that may last me another 200k+ miles before it goes out again.

Best case, is I caught this problem early, and the newly repaired and tested ECM keeps me from being stranded on the side of the road somewhere remote, which is where I tend to go. (this truck is my Overland rig).

Open to any and all feedback if anyone else has something to add.

I'm documenting everything here in the hopes it helps another poor ******* with the same P0122 error code and a truck about to be disabled.

 

[KevinsOffroad]

You seem to understand all this. Have you read/done this?

P0122 APPS Sensor Signal Voltage Too Low

DTC P0122: APP SENSOR SIGNAL VOLTAGE TOO LOW Monitor & Set Conditions Accelerator Pedal Position Sensor (APPS) voltage is monitored when the engine is running. DTC may be stored if low voltage is detected on APPS signal circuit or low voltage is detected between Engine Control Module (ECM) an...

mopar1973man.com

Yes, that's the "Moparman's instructions" I was referring to in my previous posts. All tested out until I got to Step 6:

"6. Turn ignition off. Ensure APPS connector is still disconnected. Disconnect ECM harness connector. ECM is located on driver's side of the engine, just in front of fuel transfer pump and contains a 50-pin connector. Check Dark Blue/White wire for continuity between terminal No. 5 on APPS harness connector and terminal No. 31 on ECM harness connector. If continuity does not exist, repair open in Dark Blue/White wire. If continuity exists, replace and program the ECM."

I verified that the DB/WH wire and the BK/YL wires from the ECM harness to the APPS harness were intact, and not shorted...they both pass continuity, meaning the harness is NOT the issue.

That leaves the ECM, it would appear...?

 

[bigfish95971]

Did you state above that the apps pin #3 was set at .63 volts. If so try setting it down to .5v where it belongs. Do apps reset afterwards. If it is not adjustable by loosening the torx screws on back it is the wrong apps, maybe a Timbo if it has a pigtail. What is the set voltage written on the apps or ECM?

 

[KevinsOffroad]

Did you state above that the apps pin #3 was set at .63 volts. If so try setting it down to .5v where it belongs. Do apps reset afterwards. If it is not adjustable by loosening the torx screws on back it is the wrong apps, maybe a Timbo if it has a pigtail. What is the set voltage written on the apps or ECM?

I'm getting a smooth transition on pin 3 from 0.48v. to 3.68v. at WOT

APPS looks to be a factory Mopar, p/n 56028184AB | 9323RF | 0.613 VDC

 

[bigfish95971]

Here is something you can do to check the ECM for intermittent issue. Probe the wire/plug at the apps or ECM plug and hook up jumper wire,about 6 ft, and run it to the cab to your hand held voltmeter. and see if it holds steady 5v.

But, If you have a delayed WTS light, do the $200 repair.Just for info, UPS is only delivering 3 days a week to my house. I can even reach a manager to *****. Skipping Monday and Wednesday, just leaving packages sit in their warehouse not moving, 20 miles away, and I am one mile from the highway they travel every day.

 

[KevinsOffroad]

Here is something you can do to check the ECM for intermittent issue. Probe the wire/plug at the apps or ECM plug and hook up jumper wire,about 6 ft, and run it to the cab to your hand held voltmeter. and see if it holds steady 5v.

But, If you have a delayed WTS light, do the $200 repair.Just for info, UPS is only delivering 3 days a week to my house. I can even reach a manager to *. Skipping Monday and Wednesday, just leaving packages sit in their warehouse not moving, 20 miles away, and I am one mile from the highway they travel every day.

WTS light operating normally...2sec when warm, maybe as much as 15sec (or so?) this morning when it was 45*F out. Does that sound normal?

T3 on APPS harness reads 0.48 with ignition switch at RUN. When I start the truck, it drops down to around 0.195~0.205v at idle. I didn't expect that.

T5 on APPS harness reads 5.01v. with ignition switch at RUN. When I start the truck, it drops slightly to 4.95v, but at around 2100 RPM, the voltage falls off QUICKLY, to 4.20v. and I saw it as low as 3.85v when jabbing the throttle, and then the CEL illuminated again after the voltage dropped.

What'cha thinking THAT sounds like...?

Interesting anomaly.

 

[bigfish95971]

I am not sure about the 5v power circuit, it is probably fine. But the .5v idle voltage dropping to .2v is a problem and the reason for your code. It should stay at .5v plus throttle input.
What I don't know is why and from where it is dropping. maybe it is a bad apps. Do you have an old one you can put on it? Otherwise I would get the one from Rockauto and replace it. I believe it is more likely the apps than the ECM at that point. But it would not hurt to get the opinion of the guy at ACS.

 

[KevinsOffroad]

I am not sure about the 5v power circuit, it is probably fine. But the .5v idle voltage dropping to .2v is a problem and the reason for your code. It should stay at .5v plus throttle input.
What I don't know is why and from where it is dropping. maybe it is a bad apps. Do you have an old one you can put on it? Otherwise I would get the one from Rockauto and replace it. I believe it is more likely the apps than the ECM at that point. But it would not hurt to get the opinion of the guy at ACS.

Yeah, it's a headscratcher. The fact that I'm getting a smooth transition on pin 3 from 0.48v. to 3.68v. at WOT WITHOUT the connections, indicates to me that the APPS MIGHT be OK...but the thought occured to me that the only power source the APPS gets is from the ECM...and if the voltage is dropping at a certain RPM, it may not be a short in the APPS that's causing it...and/or BOTH are bad...perhaps a bad APPS took out the power supply on the ECM, causing that partial short I'm seeing when the ECM harness is plugged in.

Chain reaction, maybe?

I'm going to pull the ECM this morning and ship it overnight to ACS and pay the rush fee...hope to get it back Tuesday. My Wells APPS from RockAuto is not going to be here in time for Tuesday, so I'll see if I can source one locally (Phoenix AZ)

 

[bigfish95971]

You can get them locally in store brands like Duralast and Carquest but they will run $160 to $260. UPS and USPS run 5 days a week . I would hold of a day or two and try the APPS before spending $300 on the ECM.

 

[KevinsOffroad]

You can get them locally in store brands like Duralast and Carquest but they will run $160 to $260. UPS and USPS run 5 days a week . I would hold of a day or two and try the APPS before spending $300 on the ECM.

I have a trip coming up next week, which I need the truck for...so I sent the ECM out on Friday. Demetrius at ACS told me that the computers are only lasting 200k miles or so, and my truck has almost 215k on it. Hopefully it's not money poorly spent...but I do feel like I'm going to bite the bullet and get the Wells APPS at whatever the cost locally, and swap it out at the same time to "protect my investment" on the ECM, and also give me better chances at solving this problem.

As far as I can tell, there was a short inside the ECM...and the fact that the voltage dropped measurably (and set of the CEL again...) at 2100rpm, tells me that ONE of the two is bad...maybe both.