What does it mean?
P1626 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Data-Bus Drive Train Missing Message From Transmission Control Module .
Symptoms
- MIL (check engine lamp) on with a transmission warning lamp
- Harsh, delayed or missing shifts, or the gearbox falling into limp
- Shifts feel like a jolt because engine torque reduction during shifting is lost
- Gear position display blank or dashed in the cluster
- Cruise control unavailable
- Symptoms coming and going with temperature, vibration or road bumps
Likely causes
- TCM (transmission control module) in a fault state and not transmitting its normal message
- Open circuit or high resistance on a bus wire to the transmission module, often at the gearbox connector
- Water or oil intrusion and corrosion in the transmission harness connector
- Low supply voltage or a poor ground at the TCM causing intermittent dropouts
- Another module disturbing bus timing or loading the network
- Coding or software mismatch after a gearbox or module replacement
- Bus termination resistance out of specification
How to fix it
- Read every module and note whether the TCM answers at all and what codes it holds
- Measure TCM supply voltage and ground under load; intermittent power is a frequent cause of dropped messages
- Test the bus lines at the transmission connector for resistance, open circuits and shorts to power or ground
- Open the gearbox harness connector and inspect for oil wicking up the wires, moisture and corroded pins
- Wiggle-test the harness along the gearbox and through the bulkhead while monitoring for the fault to appear
- Confirm the TCM coding and software match the vehicle after any replacement work
- Repair the harness first and replace or code the TCM only when wiring and supply are proven good