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Poor Fuel Mileage and Low Power

BMC330
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Mopar1973Man

Mopar1973Man

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It might work for the test to verify but not a replacement. So it worth it for the testing aspect but create its own issues. Like I've found mismatched PCM vs ECM will cause communication problems as well. For what we want it for and testing the APPS sensor just plugging in the donor PCM and turn the key on and cycling the throttle up and own with your scan tool will tell us if its the problem.

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BMC330

BMC330

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I have learned a lesson on this adventure.  Mechanical problems are much more enjoyable to work on.   Wiring issues are really a pain.  I have used a Fluke Meter more in the past two days than in my entire life.

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RipnRam99

RipnRam99

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I have been having some similar issues with power/boost/milage... Lots of good information here! 

One thing that I was not aware of is that the ECM and PCM must be matched to the options in the truck... As I am just about a day or two from beginning to tear down the truck I wrecked, to pull out modified motor/trans, and replace stock drive train in the newer (to me, both 1999s) truck... I am wondering if I should swap ECM & PCM as well? Would I need to use my old instrument cluster as well? I think they are linked.

Sorry if I'm side tracking this thread a little. I am just trying to get a big picture game plan together, and organize this potential fiasco as best I can.

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BMC330

BMC330

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I called auto computer spectlist.  They said the PCM had no bearing on the APPS voltage being erratic.  It was the ECU that controlled the APPS. 

 

Im confused as to is the issue in the PCM or the ECM.

 

I know PCM has something to do with the APPS due to unpluging the PCM corrects my erratic APPS.

 

Which should i be looking to replace PCM or ECU?

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Mopar1973Man

Mopar1973Man

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2 minutes ago, BMC330 said:

I called auto computer spectlist.  They said the PCM had no bearing on the APPS voltage being erratic.  It was the ECU that controlled the APPS. 

 

Im confused as to is the issue in the PCM or the ECM.

 

I know PCM has something to do with the APPS due to unpluging the PCM corrects my erratic APPS.

 

Which should i be looking to replace PCM or ECU?

 

Automatic or manual?

 

If you are manual like me then the PCM does control the APPS sensor line because there is no vacuum cruise motor like the automatics use. So my PCM is directly connected to the ECM sharing the APPS sensor wires. Where automatics still share it but only for sense of how much TPS signal for shift signal. If you unplugged the PCM and the signal is now stable it still lean back on the fact the PCM is screwing up the signal. 

 

Look at C1 pin 22 that is APPS sensor signal.

2002-Dodge-Wiring-Pg1.jpg

 

Now look here at Pin 28... Yes, they are connected and share the signal.

2002-Dodge-Wiring-Pg3.jpg

 

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RipnRam99

RipnRam99

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2 hours ago, Mopar1973Man said:

I would keep your pair of ECM and PCM. If the other donor truck is a matching truck with same options then I would take the ECM and PCM for spares.

What options should I pay attention to? So far, the only difference I see is the donor truck has posi rear axle, and the new truck doesn't... Also little things like my doors don't auto lock at 10mph, and the O/D on-off button on the end of the shifter doesn't do anything. No light on the dash either. Even when I first turn the key to the on position... Other than that, everything is the same, as far as I can tell... Someone deleted badges on new truck. Old truck was an SLT.

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RipnRam99

RipnRam99

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1 minute ago, Mopar1973Man said:

Electrical options. Anything different between the PCM options and ECM options. 

I have no idea what options those would be... 

Like I said... The only thing I see that is different is the O/D on-off button... It's not marked on the shifter, and it does nothing when I push the button... The donor trucks is marked, and it down shifts to 3rd when you push it, and the dash has a O/D off light ... Ever heard of an auto truck not having the O/D off option?

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  • 2 weeks later...
BMC330

BMC330

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Got new PCM in today.  Cleaned ground and installed the new PCM.  I still have no change in the truck.  No power above about 1/8 peddle.  

 

I do not have the scanner to plug into the truck at this time,  it belongs to my nephew and he has to use at his shop during the week.  It will be this weekend before I can get it back.

 

I have new codes with the new PCM by key display.

 

P0122

P1698

P0522

P0123

P1295

 

Still chasing the problem.

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  • 2 weeks later...
BMC330

BMC330

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On 4/19/2018 at 8:38 PM, Mopar1973Man said:

 

 

 

 

Got new PCM in today.  Cleaned ground and installed the new PCM.  I still have no change in the truck.  No power above about 1/8 peddle.  

 

I do not have the scanner to plug into the truck at this time,  it belongs to my nephew and he has to use at his shop during the week.  It will be this weekend before I can get it back.

 

I have new codes with the new PCM by key display.

 

P0122

P1698

P0522

P0123

P1295

 

Still chasing the problem.

 

 

Completed APPS voltage to high test.  At the end I got to replace ECM.  I was allowed to borrow an ECM from a truck very close to mine.  Only thing I could find was 2WD where mine is 4WD.  The other ECM did not change anything on my performance.

 

I purchased a Load Pro.  I am about to start load testing ground wires.  Maybe I will find the problem today.

 

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