What does it mean?
P1767 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: A/T Transmission Relay Circuit Malfunction .
Symptoms
- MIL (check engine lamp) is on and the transmission is stuck in one gear, usually with no upshifts
- Harsh engagement when selecting drive or reverse
- Shifting suddenly stops mid-drive and then works normally again after an ignition cycle
- No torque converter lockup, so engine speed stays high on the highway and fuel use climbs
- On some units reverse is missing entirely
- Several transmission solenoid codes appear together, all pointing at the same supply
Likely causes
- Transmission control relay failed: burnt contacts, high contact resistance or an open coil
- Corroded, loose or heat-spread terminals in the relay socket of the underhood fuse box
- Blown fuse in the solenoid supply feed, or a fuse with a cracked element that opens when hot
- A shorted solenoid pulling the supply line down, so the module sees the relay output collapse
- Open or shorted relay control wire between the module and the relay coil, or a missing coil ground
- Water intrusion into the fuse and relay box after washing or a blocked cowl drain
- Failed relay driver output in the control module
How to fix it
- Check the transmission fuses and the relay itself for a blown element or discoloured housing
- Substitute an identical known-good relay from the same box and see whether the behaviour changes
- Measure voltage on the solenoid supply pin at the transmission connector with the ignition on and the engine running
- Inspect the relay socket for melted plastic, spread blades and green corrosion; repair the socket rather than only the relay
- Verify the module's relay control output with a test light or scope while the relay is commanded
- Before fitting another relay, check the solenoid supply line for a short to ground that may have burnt the first one
- Repair the harness or fuse box, refit the relay and confirm operation with the system under load