PRNDL yellow, truck dies after start.

2016 Ram Power Wagon, all stock, around 168,000 miles on her. So, about a month ago, I started to get a rough idle in my truck. Then I got a low battery voltage message. I scanned the truck for codes and got a p0207 open circuit. The exhaust also had a rich smell to it, and I would see a small bit of smoke on startup sometimes, not all the time. About a week later I took it to AutoZone to test the battery and alternator and they said it all checked out good. About a week later, the truck died in the middle of the road. PRNDL were now yellow also and a check electronic throttle control system symbol/message. I cleaned the throttle body; however, it wasn’t very dirty. Still no luck. The truck would start but die after a second or 2. Took it to the dealership and was told I needed a new PCM. New PCM was installed, and the truck was good. So, I thought. About a week later I got the low battery voltage again. Dealership said I needed a new alternator. I installed a new alternator and roughly 2 days later I got the low battery voltage message again. Now, today, 17 Feb 2023, as I pulled into my work parking lot, PRNDL are yellow again and truck dies after 1 to 2 seconds again. I’m completely stumped here. Not sure if I have a short somewhere, bad ground or what. Any help would be great.

You said a month ago it started having a rough idle and smells rich. My was your first thought to check the spark plug. When were they last replaced? When they were replaced what type were they? Copper, platinum, iridium will determine how long the new plug are ment to last. Bad idle can cause voltage problems if the alternator is not spinning at the rpm the computer expects. Stealerships always says pcm when they don't know what's wrong and they don't want you going anywhere else because they are the only ones that can properly program the computer. When the engine is running bad and/or electrical problems any light might come on on the dash. The light may not be the cause but just an effect.

My husband's camry had a similar issue where it would randomly die. Almost caused a crash when pulling out into traffic. I started with the basics. Cleaned throttle body, new plugs and disconnected the computer to unlearn and trim values. It has never died again.

I bought the truck in July of 2021 with right at 45,000 miles. It has whatever spark plugs were in it then. I guess I'll be looking at the plugs then, it can't hurt. I've already cleaned the throttle body so I know that's good. I will also disconnect the computer like you said also. During the code scan, all the fuel injector misfire numbers were good except for number 7 which had at the time 362 count. So I might as well replace it with the new one I bought when this started,or what do you think?

If you can afford it, replace all the plugs. If i remember correctly the stock ones are only made to last 100,000 miles. You are in major need of new plugs, even if the computer doesn't detect a missfire you will be surprised. If you want just replace the ones that are misfiring at this time while you are diagnosing the issue. You very well could have an electrical issue or bad sensor somewhere.

The hardest thing is to have mutiple things wrong because its hard to know what to replace and when something is replaced whether it fixed anything.

Have you checked the O2 sensors?

O2 sensors are still good. I suppose I can at least change the number seven plug right now since that’s the one with the misfire, also which type of plug do you recommend because I see all kinds of information out there about them?

ryanpaulaf1 said:

O2 sensors are still good. I suppose I can at least change the number seven plug right now since that’s the one with the misfire, also which type of plug do you recommend because I see all kinds of information out there about them?

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The way I would do it it take one out and see what the factory uses and buy the same thing. If I had to guess they are either platinum or iridium made by ngk or champion. Mopar may have its own branded plugs but the partnumber will cross over to another brand. Don't forget hemis have 2 plugs per cylinder. In the event that plugs don't change the misfire, switch 5 and 7 coil and see what that does.

Wait…you put 123,000 miles on it in less than 2 years ?!

oh no, my fault, I meant she has a little over 68K. Good catch lol.

BowerPower said:

You said a month ago it started having a rough idle and smells rich. My was your first thought to check the spark plug. When were they last replaced? When they were replaced what type were they? Copper, platinum, iridium will determine how long the new plug are ment to last. Bad idle can cause voltage problems if the alternator is not spinning at the rpm the computer expects. Stealerships always says pcm when they don't know what's wrong and they don't want you going anywhere else because they are the only ones that can properly program the computer. When the engine is running bad and/or electrical problems any light might come on on the dash. The light may not be the cause but just an effect.

My husband's camry had a similar issue where it would randomly die. Almost caused a crash when pulling out into traffic. I started with the basics. Cleaned throttle body, new plugs and disconnected the computer to unlearn and trim values. It has never died again.

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What do you mean by disconnect the computer? Would disconnecting the battery so the same thing?

So when I tried to go home, it actually started and was running, albeit a little rough though. The service Electronic throttle control light was flashing also. When I put in in drive, \i got about 20 feet and she died. I think I'm gonna go back tomorrow, and replace the #7 fuel injector and the #7 spark plugs first and see what happens. Fingers crossed.

olyelr said:

Wait…you put 123,000 miles on it in less than 2 years ?!

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That makes more sense. I have seen people do that. I guess I should have questioned it.

I wouldn't worry about the injector. It won't hurt to do it. I have never seen a daily driver car need an injector. I'm sure it happens but it's rare. What you are describing is running rich and isn't a fuel problem.

You might have a bad throttle body and or bad peddle sensor. The only way to determine which one it is, look at a scan too and watch the values of the peddle sensor and throttle body while you slowly press the gas pedal. This won't cause a misfire but can cause rough idle especially if it is the throttle body. The computer constantly moves the throttle body at idle.

By disconnecting the computer, I do mean battery. I think I disconnected it for an hour or so. The computer will have capacitors that take time to discharge. You want the computer to forget all of its short term fuel and throttle body learn. Over time the computer will learn to compensate for a dirty throttle body and bad spark plugs, etc. I can't guarantee it's your problem but it's free to do and worth a try.

Thanks for the suggestions. I’ll give it a shot tomorrow. Will keep the post updated as I can.

So far I’ve done the following, swap fuel injectors, five and seven, and it showed no issues. I still installed the new fuel injector into number seven. It still shows misfires on number seven on the scanner. I also cleaned the throttle body, replaced cylinder 7 spark plugs and left the battery disconnected for well over an hour. The truck will start and run, but runs rough and the service electronic throttle body light is still blinking. Also, when I turned on my scanner, it showed that every cylinder had an open circuit, so I have no clue what to do other than bring it to the dealership Monday, unfortunately. This is completely out of my ability to figure it out. The first picture is of cylinder 7.

How did you confirm the O2 sensors were good? Both upstream and downstream? I’d start looking at fuel trims before loading the parts cannon again.

KoboldTaco said:

How did you confirm the O2 sensors were good? Both upstream and downstream? I’d start looking at fuel trims before loading the parts cannon again.

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I can not speak to injector open circuit. I have never ran into that before, but... upon initial start up the computer does not use the O2 sensor. Upstream sensors are the only one use to affect air/fuel. Downstream are only there to see if the catalytic converters are working.

It is my understanding, when started, the computer is in open loop and uses: coolant temp, MAF/MAP, IAC (throttle body), etc... to run the engine. The Computer uses close loop when warm and cruising. Then it uses O2 sensors to get best fuel economy.

To make a long story short, if it is running bad when first started and engine is cold, O2 sensors are not the issue. I am thinking that the accelerator pedal or throttle body are bad. It looks like the computer is dumping fuel as if your hitting the gas but throttle body is closed. I wouldn't want to throw parts at it. I would need to see some real time value before I were to do anything.

BowerPower said:

I can not speak to injector open circuit. I have never ran into that before, but... upon initial start up the computer does not use the O2 sensor. Upstream sensors are the only one use to affect air/fuel. Downstream are only there to see if the catalytic converters are working.

It is my understanding, when started, the computer is in open loop and uses: coolant temp, MAF/MAP, IAC (throttle body), etc... to run the engine. The Computer uses close loop when warm and cruising. Then it uses O2 sensors to get best fuel economy.

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Howdy - BowerPower - yup agreed. Looking at fuel trims may indicate a closed loop condition when cold and I've seen it cause the misbehavior the OP is stating or open/closed loop issues mismatch between banks also. Just a thought to look there if the tool they have can pull that data.

If we rule out fuel issues, going in a bit deeper since the injector swap proved it stayed with 7, I think the only way to catch this is to use a PICO scope or another form of data analysis tool to check if you are losing power (partial, full etc) at the injector itself. Then you can start to trace it back to the ECM, or start there to review the injector firing behavior and perhaps catch a sly sneaky but difficult-to-find wiring issue. A probe at the ECM and a probe at the injector connector (and comparison) might give a fighting chance to nail down if it's a wiring issue or not.

KoboldTaco said:

Howdy - BowerPower - yup agreed. Looking at fuel trims may indicate a closed loop condition when cold and I've seen it cause the misbehavior the OP is stating or open/closed loop issues mismatch between banks also. Just a thought to look there if the tool they have can pull that data.

If we rule out fuel issues, going in a bit deeper since the injector swap proved it stayed with 7, I think the only way to catch this is to use a PICO scope or another form of data analysis tool to check if you are losing power (partial, full etc) at the injector itself. Then you can start to trace it back to the ECM, or start there to review the injector firing behavior and perhaps catch a sly sneaky but difficult-to-find wiring issue. A probe at the ECM and a probe at the injector connector (and comparison) might give a fighting chance to nail down if it's a wiring issue or not.

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That's interesting, I never ran into a vehicle that has gotten closed and open loop mixed up. I also stopped being a mechanic years ago so my knowledge is limited. When I was a mechanic, we had a few cars that we could not fix a miss and had to send them to the dealer. OP needs to keep us informed on the process and fix. I want to keep this one in my book of knowledge for future use.

You wouldn't think it was the ecm since it was just replaced. If he has a wiring issue between ecm and injector that could over a few weeks hurt the ecm and cause it to go back to running bad.

BowerPower said:

That's interesting, I never ran into a vehicle that has gotten closed and open loop mixed up. I also stopped being a mechanic years ago so my knowledge is limited. When I was a mechanic, we had a few cars that we could not fix a miss and had to send them to the dealer. OP needs to keep us informed on the process and fix. I want to keep this one in my book of knowledge for future use.

You wouldn't think it was the ecm since it was just replaced. If he has a wiring issue between ecm and injector that could over a few weeks hurt the ecm and cause it to go back to running bad.

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I’m looking forward to the resolution on this one as well. Since my moto crash, I’ve not been able to actively wrench so this forum and fun discussions such as this are great medicine!

Clarification! Does the vehicle stall when placed in R,D or L and not in P or N? If yes, I suspect an issue with the TC lock-up. Backing up, make sure the dealer credits you, at least the labor, for replacing unnecessary parts!