My 99 started as a 4 cylinder 5 speed truck, and the PO swapped in an obd 1 5.2 from a dodge ram and repinned the pcm connectors. and said it had a durango v8 pcm. it has a problem where it retards the timing to 0 degrees when at WOT below 35mph. but all the gauges work. i purchased a 97 dodge ram 5.2 MT pcm and when installed it runs perfect. full power and all. idles good, responsive. but I get the "no bus" and no gauges work. ive been tracing wires and reading diagrams but cant seem to figure it out. no meaningful dtc's come up, just evap, N/P switch, governor pressure, trans relay. why would an auto ram, and auto durango pcm allow the gauges to work but the manual 97 pcm doesnt? cluster codes i get are 920 921 and 999(only with the 97 ram mt pcm) any ideas?

 

what a disaster. "repinned the PCM connectors" severely frightens me. Especially if they tried to use the OBD1 harness.

Me personally? I'd start TF over. But i also have more knowledge than most...

920 The cluster is not receiving a vehicle speed message from the PCM.
1. Check the PCM software level and reflash if required.

2. Use a DRB scan tool to verify that the vehicle speed message is being sent by the PCM.

921 The cluster is not receiving a distance pulse message from the PCM.
1. Check the PCM software level and reflash if required.

2. Use a DRB scan tool to verify that the distance pulse message is being sent by the PCM.

999 An error has been discovered.
1. Record the failure message.

2. Depress the trip odometer reset button to continue the Self-Diagnostic Test.

 

i guess "repinned" is kinda scary just saying. but it appears as though he grabbed 2 of the 3 connector pig tails and just matched up the colors on the truck harness to the pcm connector wires. it has a newer "correct" harness but every single sensor was cut and spliced. because the sensors were the obd 1 '95 sensors. from what I can tell. Do you know what path or pin the pcm is supposed to send the distance pulse message and vehicle speed? Its strange how 1 dodge ram pcm will allow the gauges to function and then the other will not. Seems like they would both output the same info to the cluster. Unless '97 ram pcm's did not have the same cluster output?

 

The problem is, between 97 and 98, Dodge changed how everything works. You need a pcm, and harness, from a 98 or 99 truck. You won't get the cluster to work properly with the 96 PCM, because it simply does not know what to tell the cluster, it doesn't even know it is SUPPOSED to tell the cluster.......

 

And the fact that OP says the cluster works fine with the hacked up OBD1/96 PCM tells me that there's some seriously F'd up stuff in that harness.

 

Wonder if the dakotas made the switch the the Central timer module feller later in life?

 

Pretty sure the CTM was there in 97, originally mounted next to the glovebox / near the infinity amp until 00 when it went to the driver footwell