PCM need to be programmed?

1996 DODGE RAM
190,000 MILES
Avatar
DNJFUN13@GMAIL.COM
  • MEMBER
  • 1 POST
Replaced fuel pump, crankshaft sensor, new plugs and wires. No start. Put in a PCM from another dodge truck. Ran for 30 min until I put it in gear. Put back the original PCM and now no fuel or spark. Does PCM need to be programmed for that specific model or can I just buy a new one and put it in? I pondering if it’s the PCM or if it could be something else
Apr 22, 2026 at 10:34 AM
Advertisement
Avatar
CARADIODOC
  • CERTIFIED EXPERT
  • 34,308 POSTS
What's the rest of the story with the replacement computer? Any time power is lost to it, meaning disconnecting the battery or the computer, you have to do a relearn for "minimum throttle". Until that is done, idle speed will be too low. Common symptoms are the engine will tend to stall at stop signs, and it may not start unless you hold the accelerator pedal down 1/4". You also won't get the nice idle flare-up to 1500 rpm at start-up.

Minimum throttle is the only learned thing that doesn't occur on its own. You have to drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the pedals.
Apr 22, 2026 at 12:20 PM
Avatar
DNJFUN13@GMAIL.COM
  • MEMBER
  • 1 POST
The truck was running until I would put it into gear. At which point I decided to put the new computer in. It ran for 30 minutes and then I shut it off. And now I cannot get any spark or fuel. I put the original PCM back in there and still the same thing. I’ve really narrowed it down to being the computer however, I don’t know if those PCM for that year of Dodge need to be programmed or if I can just order one off-line and put it in.
Apr 23, 2026 at 8:25 AM
Advertisement
Avatar
CARADIODOC
  • CERTIFIED EXPERT
  • 34,308 POSTS
If it ran for thirty minutes, it doesn't need to be programmed. You're still going to have to do the minimum throttle relearn at some point, otherwise idle speed will be too low.

Normally the place to start is by reading and recording any diagnostic fault codes, but that won't work now. They get erased when the Engine Computer is unplugged. With no spark and fuel, the most common suspects are the crankshaft position sensor and the camshaft position sensor. It is very common for fault codes for them to not set just from cranking the engine, so don't look at a lack of a related code to mean those sensors are okay. They normally need more time for a missing signal to be detected, as in when a stalled engine is coasting to a stop. If you do want to check the fault codes, Chrysler made doing that yourself much easier than any other manufacturer. Cycle the ignition switch from "off" to "run" three times within five seconds, without cranking the engine. Leave it in "run", then observe the fault code numbers in the odometer display. There's two other ways to proceed without fault codes.

The best way is to view the automatic shutdown, (ASD) rely status on a scanner. It should turn on for one second when the ignition switch is turned to "run", then it turns on again during engine rotation, (cranking or running). The computer needs to see signals coming from the two sensors during cranking, then it turns on the ASD relay which sends power to the injectors, ignition coil(s), fuel pump or pump relay, and a few other places.

The other way to check ASD relay operation is to connect a test light to the wire that's the same color at any injector, any ignition coil, or to either of the two smaller terminals on the back of the alternator. Most commonly that's a dark green / orange wire. Back-probe through the rubber weather seal alongside the wire. Prop the test light so you can see it from inside the truck, or have a helper run the ignition switch for you. You should see the test light turn on full brightness for one second when the ignition switch is turned to "run". That proves the ASD relay and circuity are okay, and the computer has control of that relay. Next, the light should turn on again when the engine is being cranked. If it does not, those two sensors are suspect. At that point you need the scanner to view live sensor data and see what those sensors are listed with. On Chrysler's DRB 3 scanner, each sensor is listed with a "No" or "Present" during cranking. Aftermarket scanners have a similar way to show whether those signals are showing up.

Let me know how far this gets you.
Apr 23, 2026 at 3:24 PM