Hi All,

I have 01 ram 1500 with 190,000 miles on it and since COVID it hasn’t been driven much but now it’s acting up. When I try to start it up; it starts and dies. I have to give it gas for it stay running, it won’t idle on its own unless you help it idle for about 15 mins. Also the speedometer and tachometer sometimes will stop working for a second and then they will pop back to life. When driving the voltage meter will randomly spike past 18 volts and will come back down after a few minutes then will randomly do it a again but never while idling. I’ve replaced the alternator, the positive cable going from the battery to the fuse box and then to the alternator, and the TPS sensor. The grounds all look fine with no corrosion. It’s the PCM or something completely different?

 

Voltage regulator is in the PCM.... So, real possibility PCM is on its way out.

 

Is that also what causes the speedo and tach to occasionally stop working?

 

Maybe.....

On your truck, just about every gauge in the dash gets its clue from the PCM, including the gas gauge...... If it is only the tach and speedo, it may be a cluster issues as well. Check connections first.

 

I’m going to replace the PCM. Found one from autozone for $190 and need to provide the vin and mileage. After that comes in, is it plug and play? Is there anything I’m missing in this process?

 

Nope. If it is properly programmed, take out the old one, put in the new one, hook up the battery, and drive away.

 

I bought an OEM PCM from eBay without having to flash, or program it. It was plug n’ play.

 

Same here for my '96 Ram, but some later years may need flashing to update the VIN to match the truck's VIN. For my swap, I made sure the PCM part number of the PCM on my truck matched with the one I purchased.

 

Update: Replaced the PCM with the one ordered from AutoZone and was programmed with the mileage and vin #. Still having the same issue with the voltage spiking while driving and the speedo dropping to zero. Is the alternator bad? Did I receive a bad PCM?

I think I am going to order one of the OBDII readers so I can see what is actually going on with the dash.

On a positive note: it no longer has issues with idling.

 

2000 1500 5.9 v8 single cab short bed sport 2wd auto
sometimes the speedo, sometimes the tach on mine will b sittin at 0 til its fully warmed up, or if I give it a slight love tap on the cluster face. Not all the time, just randomly. My pcm is currently fkd at the moment tho so it's not gonna b doin any of that til i fix that issue. When ur pcm goes, it's not gonna start. Itll crank all day but wont start. Also, itll chime (6 times i think) n then the odometer will flash n then say "no bus". If u have a package w the overhead electronic console, that will display "CCD" and none of ur gauges will come on. U wont have a check engine light because the truck cant communicate w the pcm ("no bus" = no communication) to tell it to throw a code/illuminate the CEL.
hope that helps in some way