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1998 PCM - replaced - still not fixed?

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1998 PCM - replaced - still not fixed?

  #1  
Old 04-12-2019, 12:01 PM
zoochy
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Default 1998 PCM - replaced - still not fixed?

I bought a new PCM from these guys:

www.fs1inc.com

Suppose to be plug and play. I installed it and it didn't fix my issues.



What doesn't work:

- gauges do not move
- air heater grids do not activate
- alternator does not charge the battery
- odometer flashes same number
- (automatic transmission) Drive position = 3rd gear; positon 1 and 2 = 2nd gear (I think)
- fuel tank empty light comes on
-ABS and Park Brake light comes on


Gauge check/display 'C' codes:

920 - cluster not receiving vehicle speed from PCM
921 - cluster not receiving distance pulse from PCM
999 - error detected

So, basically, the PCM is not talking to the cluster

The PCM grounds tested good.
CCD Bus has 2.46V

The dealership thinks I might have to sync the PCM to the truck, even though the unit is supposed to be plug and go. I think they just want to charge me to try it?

Has anybody had a similar experience?

What else could be wrong?
 
  #2  
Old 04-12-2019, 12:17 PM
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HeyYou
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PCM needs to be flashed to the correct VIN, and that's it. Nothing else needs to happen for it to work.

Is the PCM getting power on the correct wires? You can download the service manual for your truck from here.
 
  #3  
Old 04-12-2019, 12:51 PM
DerTruck
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Please clarify: You had the same symptoms with the old PCM or these are all new ? Why did you change the PCM in the first place ?
 
  #4  
Old 04-12-2019, 01:57 PM
zoochy
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Exact same symptoms with the new and old PCM

I provided the PCM manufacturer with my VIN, which they claim to have programmed in.

Voltage to the PCM and Grounds are good.

I bought a new PCM because the The Dealership claimed "all conditions are due to no response from PCM"

So frustrating.
 

Last edited by zoochy; 04-12-2019 at 08:08 PM.
  #5  
Old 04-12-2019, 02:25 PM
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Wonder if its the CTM that failed.... after all, it is responsible for all communication in the truck. I would expect a 'no bus' error if that were the case though.
 
  #6  
Old 04-12-2019, 03:06 PM
zoochy
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The intermittent wipe control and the driver door open warning chime (when the lights are on) still work though, which are controlled by the CTM?
 
  #7  
Old 04-12-2019, 04:30 PM
MoparFanatic21
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I would check fuses and wiring. I'd you know somebody with a good scanner and grew connects to your truck, he can tell if it has your VIN programmed into it
 
  #8  
Old 04-12-2019, 05:10 PM
DerTruck
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I doubt the CTM is the culprit, from what I gathered there are two versions of the CTM, base and highline/premium. Base doesn't even have CCD connections, only highline/premium has. I'd start with checking joint connector 7 under the dash where all the CCD devices are connected together. Check the wiring from there (pin 14 and 11) to the PCM (note the 98 FSM available on here shows the PCM twice, the top right device should be the overhead console though).

I'm still puzzled though that a problem with the CCD bus would affect the intake heaters etc. Could well be the CCD bus is a symptom not the cause. As already suggested look at power and ground for the PCM.
 
  #9  
Old 04-12-2019, 06:49 PM
zoochy
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Might have found something...
On page 8W - 80 - 14 of the service manual
Plug C2 which is white on my truck not black like the service manual suggests
CAV 31 - K7 180 - 5 volt supply has no power to it when the ignition is on.... (I didn't wanna start the truck as the air filter was off)
Should that have power? Or does that voltage vary with the throttle position?
 

Last edited by zoochy; 04-12-2019 at 06:53 PM.
  #10  
Old 04-12-2019, 07:25 PM
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Nope, that pin is supply. There should be 5 volts there with ignition on.
 

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