What does code P1691 mean?

Q: What does code P1691 mean?

Coolant Gauge Circuit Voltage Low. P1691 on a GM vehicle means the instrument cluster or body control module has detected a low voltage condition on the coolant temperature gauge circuit, which is the signal wire that drives the temperature needle or digital display. The computer is not reporting an engine coolant temperature sensor fault; it is specifically flagging that the gauge circuit voltage has dropped below the expected range, which usually points to a wiring, connection, or gauge head problem rather than a cooling system failure.

DTC codes / GM codes / P1691

P1691 · GMCoolant Gauge Circuit Voltage Low

P1691 on a GM vehicle means the instrument cluster or body control module has detected a low voltage condition on the coolant temperature gauge circuit, which is the signal wire that drives the temperature needle or digital display. The computer is not reporting an engine coolant temperature sensor fault; it is specifically flagging that the gauge circuit voltage has dropped below the expected range, which usually points to a wiring, connection, or gauge head problem rather than a cooling system failure.

SystemPowertrain

Code typeGM specific

SeverityLow

Fix difficultyIntermediate

AreaComputer and output circuits

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