P1637 fault code: what it means

P1637: TCM memory back-up circuit fault (learned values lost, e.g. after battery work).

Engine and gearbox (powertrain) · Keep an eye on

Usual causes, most likely first

1. battery disconnected
2. back-up fuse or wiring
3. TCM

P1637 by make

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Before you clear it

Write the code down or photograph the scanner first. A code that comes straight back after clearing points to a fault that is still there. A car whose codes were cleared just before you arrived may be hiding one: the scanner's readiness monitors show "not ready" for a while after codes are cleared.

Researched by Credov from manufacturer and workshop sources. A fault code points to where a fault may be; a workshop confirms it with a diagnosis. Browse all fault codes.