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08 Dodge ram

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03 Sep 2017 08:57 #12553 by Jlr022581
08 Dodge ram was created by Jlr022581
New to this site. Found videos on YouTube. And thought maybe I could find help here. I have a 08 Dodge Ram 1500 quad cab hemi 5.7. About three weeks ago I was driving to work everything was running fine. Then the electronic throttle body control light came on flashing along with engine light and I had no acceleration. I was able to get the truck home. I was told that my throttle body needed to be replaced so I did that. Still no change. Then a mechanic told me it was the ecm so that was replaced by one bought off the internet by carcomputerexchange. Still no change. Also I replaced the crankshaft sensor cause it was stalling on start up and throwing the code for that and that fixed the cranking hesitation. At that point I figured I needed to get someone who knows more about electronic wiring to look at it and start just throwing parts at it. So I took it to Dodge. What a damn waste of time and money that was. They do the diagnostic and tell me I need to replace the ecm, throttle body and accelerator pedal sensor. I told them I just replaced two out of the three and they told me that was all they knew to do. I have the truck home now. they cleared the codes the truck was throwing and now the only one popping up is p0520 oil pressure sensor. I changed that. Still no change. The reading on the oil pressure gauge is reading high I would say 9 constant. It is also noteworthy that before I replaced the ecm the oil pressure light was not reading at all. Then after I replaced to ecm it started reading high.

I just need the truck fixed and was willing to pay to get it fixed but I find it hard to believe that everything I have change are all bad parts. I'm lost any help or guidance would be greatly appreciated thank you.

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03 Sep 2017 11:22 #12559 by Tyler
Replied by Tyler on topic 08 Dodge ram
Cheryl, I deleted your response on accident. :blush: Somehow, your response had reposted five times, and I hit the Delete button one too many times. My mistake!


Cheryl had suggested going for codes first, which I totally agree with. Get the truck to go into limp home mode again, and see what trouble codes are stored. Something as simple as an ELM327 Bluetooth device with your phone would work. I bought this BAFX one off Amazon , and it's worked very well.

The oil pressure gauge and code are interesting... I have to wonder if the PCM you bought is incorrect for the truck, OR the programming isn't correct. Some voltage measurements at the oil pressure sensor could help answer those questions. For reference, I looked up the wiring diagram:



Backprobing with the key on, we're looking for 5V on the pink/yellow wire, something between .5V and 4.5V on the violet/grey wire, and 0V on the dark blue/dark green. Or with the sensor disconnected and the key on, 5V on the pink/yellow, 5V on the violet/grey, and 0V on the dark blue/dark green. Let us know what you find. ;-)
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03 Sep 2017 11:59 #12562 by cheryl hartkorn
Replied by cheryl hartkorn on topic 08 Dodge ram
interesting i only hit submit once

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03 Sep 2017 12:05 #12564 by Tyler
Replied by Tyler on topic 08 Dodge ram
Nah, it's not just you, I've seen it happen to other members. Not sure what happens, exactly. I've been fixing it when I see it, but I usually don't get so trigger happy. :unsure: Again, my apologies.

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03 Sep 2017 14:55 #12566 by Jlr022581
Replied by Jlr022581 on topic 08 Dodge ram
New developments have arise. I left my key in the ignition last night which drained the battery. Jumped it off and I'm getting a solid 12.46 from the battery. By the way also new battery only two weeks old. But as I got truck running I noticed the check engine light isn't on anymore like it has been since this all started. Also the only code it is reading is 0p0562 which is low voltage probably from the battery draining. Also the tech at Dodge wrote on the diagnosis that my 5 volt reference at the throttle body sensor was reading 5.89. What would make it run high? I will check the voltage readings at the oil pressure sensor and get back with the findings momentarily thank you again for the help and advice.

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03 Sep 2017 14:57 #12567 by cheryl hartkorn
Replied by cheryl hartkorn on topic 08 Dodge ram
your only reading 12.46 volts running?? thatd suggest a charging issue

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03 Sep 2017 15:02 #12568 by Jlr022581
Replied by Jlr022581 on topic 08 Dodge ram
No while it's running its reading 14.23 volts

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03 Sep 2017 15:03 #12569 by Jlr022581
Replied by Jlr022581 on topic 08 Dodge ram
Sorry I am new to this I will try to be more specific

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03 Sep 2017 15:14 #12570 by Jlr022581
Replied by Jlr022581 on topic 08 Dodge ram
Ok reading from the oil pressure sensor pink/yellow wire reading 5.81 volts violet/grey wire reading 3.94 and dark blue/ dark green reading 0 volts

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03 Sep 2017 17:05 #12572 by Tyler
Replied by Tyler on topic 08 Dodge ram
Thanks for the readings! That 5.81V is very strange - I can understand why the Dodge tech made note of it.

Do you still have the old PCM? Even if you end up causing a SKIM issue, I'd be interested to know if the old PCM produces the same high voltage.

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03 Sep 2017 17:08 #12573 by Jlr022581
Replied by Jlr022581 on topic 08 Dodge ram
No I do not had to send it to them or pay a core charge. At that time I never thought I would need it. It's my first time dealing with electrical problems. Any idea what could cause the 5 volt ref to run high like that?

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03 Sep 2017 17:11 #12574 by Jlr022581
Replied by Jlr022581 on topic 08 Dodge ram
From my understanding if it was a short to ground I wouldn't have a signal. But what about a high reading.

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03 Sep 2017 17:40 #12575 by Tyler
Replied by Tyler on topic 08 Dodge ram

From my understanding if it was a short to ground I wouldn't have a signal. But what about a high reading.


It's very unusual...Either the 5V regulator in the PCM is toast, there's a PCM ground issue, or another circuit is bleeding voltage into the reference circuit. I'll need to get home and have another look at the diagram.

Just to be clear, the oil pressure gauge weirdness wasn't there prior to the PCM replacement?

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03 Sep 2017 17:46 #12577 by Jlr022581
Replied by Jlr022581 on topic 08 Dodge ram
Correct. It worked just fine up until I lost all throttle. I have the oil pressure gauge in my truck. And it would fluctuate depending on my driving.

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04 Sep 2017 11:59 #12623 by Tyler
Replied by Tyler on topic 08 Dodge ram
So, the gauge and the throttle started at the same time? Really not trying to nitpick! :lol: Just trying to determine if the two symptoms are associated, or that the gauge thing was introduced by the PCM replacement.

For me, you've got two directions you can go. One would be to verify PCM grounds. The other would be to eliminate the 5V reference circuit as the source of the elevated voltage. We may end up doing both, depending on what you find.

Chrysler OE diagrams are nice, in that they condense PCM powers and grounds onto one page for easy testing. Check out the first page of this PDF:

File Attachment:

File Name: document4.pdf
File Size:642 KB


Grounds on pins 9, 18 and 19 of C1. Use your DVOM or incandescent test light on these while the 5V reference is doing it's 5.81V thing. 100mV or less is what we want to see.

About the 5V reference circuit, there's a couple other quick tests we can do. Because it's an electronic throttle body, there's two 5V reference circuits at work. We know one is high, but knowing the health of the other would be valuable. From what I can tell, one 5V ref (coming from pin 29 of C2) feeds APP1, the crank sensor, the oil pressure sensor and the TPS. This is the one with 5.81V on it. The other (from pin 27 of C1) feeds the MAP, CMP, and APP2.

Probably the easiest place to measure both would be at the APP. It's the yellow/pink and the pink/yellow we're interested in.



Measure both with your DVOM and let us know what you find. :cheer:
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04 Sep 2017 15:07 #12647 by Jlr022581
Replied by Jlr022581 on topic 08 Dodge ram
Ok readings at the apps sensor are PK/YL 5.86 and YL/PK 5.01 going to check the grounds next. Do I change settings on the multimeter for checking the grounds.

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04 Sep 2017 15:10 #12648 by Jlr022581
Replied by Jlr022581 on topic 08 Dodge ram
And yes the oil gauge stop working at the same time the etc light came on and went into limp mode. It all happened at once. I went from no sensor light on to etc flashing and oil gauge stopped working and check gauge light and check engine light on all at once. It was crazy.

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