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DTC codes / GM codes / P1626

P1626 · GMAnti-Theft Fuel Enable Circuit (Passkey)

P1626 on a GM vehicle means the body control module (BCM) has not received the correct fuel enable password from the vehicle anti-theft system, so it is refusing to allow the engine to start or run. The computer detected a missing or mismatched serial data message from the Passkey/Passlock module rather than a hard wiring failure in the fuel pump circuit itself.

SystemPowertrain
Code typeGM specific
SeverityMedium
Fix difficultyIntermediate
AreaComputer and output circuits

Symptoms you may notice

  • Engine cranks but will not start, or starts and stalls immediately
  • Security or anti-theft warning light illuminated or flashing on the dash
  • No symptoms besides the warning light if the fault is intermittent
  • Engine may run for a few seconds and then shut off as the fuel enable is withdrawn
  • Intermittent no-start that clears after cycling the key or waiting several minutes
  • Other electrical oddities such as delayed cranking or a dead instrument cluster

Common causes, most likely first

  1. Failed or failing Passkey/Passlock sensor in the ignition lock cylinder
  2. Worn or damaged ignition key resistor pellet or transponder key not being read
  3. Poor connection or corrosion at the BCM, ignition switch, or anti-theft module connectors
  4. Faulty body control module (BCM) not processing or sending the fuel enable signal
  5. Damaged or chafed wiring in the anti-theft serial data circuit between the lock cylinder and BCM
  6. Ignition switch wear causing intermittent loss of power to the Passkey module
  7. Aftermarket remote starter or alarm improperly installed and interfering with the factory anti-theft signal

How to diagnose and fix it

  1. Scan all modules for codes and record freeze-frame data, then clear codes and see if P1626 returns immediately
  2. Try a second known-good key and inspect the key pellet or transponder for damage or contamination
  3. Check battery voltage and perform a voltage drop test on the ignition switch and BCM power and ground circuits
  4. Inspect and wiggle-test the wiring harness at the lock cylinder, BCM, and anti-theft module for intermittent opens
  5. Perform the GM Passkey/Passlock relearn procedure with a scan tool or the manual key-on timing method
  6. Test the Passkey/Passlock sensor signal at the BCM with a multimeter while turning the key
  7. Replace the failed component only after confirming the signal is missing at the BCM, then repeat the relearn

Passkey faults that mimic fuel pump failures

  • A no-start with P1626 is often misdiagnosed as a failed fuel pump because the pump is commanded off by the BCM, so verify fuel enable before replacing pump parts.
  • A weak or failing vehicle battery can set P1626 because the BCM drops out during cranking and loses the anti-theft handshake.
  • Aftermarket remote starters and alarms are a common hidden cause because they splice into the Passkey serial data line and corrupt the fuel enable message.
  • The key resistor pellet can wear or pick up debris, so trying a spare key is a fast and free diagnostic step before any module replacement.
  • P1626 can be stored alongside communication codes such as U1000 or U1064 when the serial data bus is disturbed, pointing to a wiring or BCM issue rather than the lock cylinder.

Can I keep driving with P1626?

If the engine starts and runs normally, the fault is likely intermittent and you can drive to a repair shop, but avoid shutting the engine off in an unsafe location until it is diagnosed. If the engine cranks but will not start, do not keep cranking; have the vehicle towed because the anti-theft system is actively blocking fuel enable.

Tools that help

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Guidance is general and written for GM vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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