There is nothing more frustrating than jumping in your truck, hitting the ignition, and getting an endless crank with no fire. Or worse, having the engine stall out completely while you are on the road. If your Check Engine light is glaring at you and your truck is dead in the water, General Motors has officially identified the culprit.

According to an updated Technical Service Bulletin (PIT5687B) released in May 2026, a simple loose wiring pin is causing massive electrical headaches for owners of 2019 through 2026 Chevrolet Silverado 1500 and GMC Sierra 1500 pickups.

Which Trucks Are Affected?

This electrical gremlin specifically targets the gas-powered V6 and V8 engines. If you are running the 2.7L TurboMax or the 3.0L Duramax diesel, you are in the clear for this specific bulletin. The affected engine RPO codes include:

  • 4.3L V6 (LV3)
  • 5.3L V8 (L82 & L84)
  • 6.2L V8 (L87)
A digital screenshot of General Motors Technical Service Bulletin PIT5687B, outlining the crank no-start and stalling condition for 2019 to 2026 Chevrolet Silverado and GMC Sierra 1500 trucks.
According to official GM documentation, if your V6 or V8 truck is experiencing a crank no-start condition or throws a P16A7 or P16AF code, a loose ECM pin is likely the culprit.

The Symptoms and DTC Codes

If your truck is suffering from this wiring issue, you will likely experience one or all of the following symptoms:

  • A crank but no-start condition
  • Engine stalling while running
  • Service Engine Soon (SES) / Check Engine light illuminated

If you plug an OBD2 scanner into the diagnostic port, you will likely find codes P16A7 and/or P16AF stored in the Engine Control Module (ECM).

What is Causing the Stalling and No-Start?

It all comes down to a poor connection. The ECM needs a solid, uninterrupted power supply to keep your engine running. The GM bulletin states that power circuit 5290 at the ECM X1 connector (specifically terminal pin 49) can suffer from poor terminal tension.

In plain English: the metal pin connection is simply too loose, causing a drop in voltage or a complete loss of power to the truck’s brain.

The open engine bay of a Chevrolet Silverado 1500 V8, highlighting the Underhood Bussed Electrical Center fuse box used for electrical diagnostics.
Before assuming your ECM X1 connector needs to be re-pinned, always start your troubleshooting by testing Fuse #86 and the KR75 ignition relay inside the UBEC.

How to Fix It

If your Silverado or Sierra is still under warranty, get it on a hook and send it straight to the dealer. For the driveway mechanics trying to troubleshoot a dead truck, the official GM diagnostic procedure is straightforward:

  1. Check the Fuse: Inspect Fuse #86 (30 amp) in the Underhood Bussed Electrical Center (UBEC). If the fuse is blown, you likely have a short to ground somewhere in the wiring harness.
  2. Check the Relay: If the fuse is good, put a battery tender on the truck, turn the ignition on, and verify you have more than 12 volts at that fuse. If the voltage is low or missing, inspect the KR75 Engine Control Ignition Relay.
  3. Test the ECM Pin: If you have solid battery voltage at the UBEC, the culprit is the X1 connector down at the ECM. Technicians are instructed to perform a “terminal drag test” on pin 49. If the pin lacks drag because it is too loose, the official fix is to cut it out and crimp in a brand-new terminated lead.

Do not just shove a pick in there and try to bend the pin to make it fit tighter. Replacing the terminal lead is the only permanent, reliable fix to keep your truck running.

Join the Conversation

Has your 2019-2026 Silverado or Sierra left you stranded with a crank/no-start issue? Head over to the community and let us know if the dealer found a loose ECM pin!