Restore Peak Performance to Your 1998-1999 GMC 3500

Is your reliable GMC 3500 suddenly plagued by a persistent Check Engine Light, erratic engine behavior, or transmission shifting problems? Before you start throwing expensive parts at it, the issue might be the very brain of your truck: the Powertrain Control Module (PCM). As a technician with over two decades of experience, I’ve seen countless vehicles sidelined by a failing PCM. This isn’t just a part; it’s the central command for your engine and transmission, and when it falters, it can cause a cascade of frustrating and hard-to-diagnose issues.

This replacement 1998-1999 GMC 3500 PCM is the definitive solution to get your workhorse back on the job. We take the guesswork and high dealership costs out of the equation. Simply provide us with your vehicle’s VIN during checkout, and our experts will flash the module with the latest, most stable GM software updates specific to your truck. It arrives at your door ready for installation, saving you hundreds in programming fees and valuable time.

Common Signs of a Failing PCM

• ✔ Persistent Check Engine Light (CEL) with codes like P0601, P0602, or P0605 (Internal Control Module Memory Errors).
• ✔ Unexplained engine stalling or rough idling.
• ✔ A noticeable drop in fuel economy.
• ✔ Harsh or erratic automatic transmission shifting.
• ✔ Engine cranks but refuses to start (no-start condition).
• ✔ Failure to pass state emissions testing.
• ✔ Multiple unrelated sensor codes appearing at once.

A Straightforward Guide to Installation

1. ✔ Safety First: Disconnect the negative terminal from your truck’s battery to prevent any electrical shorts.
2. ✔ Locate the PCM: On most 1998-1999 GMC 3500 trucks, the PCM is located in the engine compartment on the driver’s side, near the fender or firewall.
3. ✔ Disconnect the Connectors: Carefully unclip and remove the large electrical harness connectors from the old module. They have locking tabs that need to be released. Avoid forcing them.
4. ✔ Remove the Old Module: Unbolt the old PCM from its mounting bracket. Keep the hardware as you may need it for the new unit.
5. ✔ Install the New PCM: Mount your new, pre-programmed PCM onto the bracket and securely fasten it.
6. ✔ Reconnect Everything: Firmly plug the harness connectors into the new module until they click into place. Reconnect the negative battery terminal.
7. ✔ Perform Security Relearn: Your vehicle may require a security relearn procedure (often called Passlock or Passkey) to recognize the new PCM. This can typically be done without special tools by cycling the key. A quick search for “GM Passlock relearn procedure” will provide the simple steps.

Verified Vehicle Compatibility

This module, identified by part number 16250279, is a direct replacement for service numbers 16250279, 09366810, and 09355699. It is guaranteed to fit the following models, provided the ID on your original module matches: