P2639
Torque Management Feedback Signal "A" Low
- Severity
- Medium
- Driving
- Drivable — book it in
Torque management feedback signal "A" is reading low - typically shorted to earth or an open circuit.
Possible causes
- CommonWiring or bus fault between the modules
- CommonCorroded connector at either module
- CommonLow battery voltage dropping a module off the bus
- CommonFault in the transmission, ABS or traction control module
- PossibleSoftware mismatch after a module replacement
- RareFailed control module input
What you might notice
- Harsh or erratic shifting
- Traction control warning light
- Reduced power
- Hesitation during gear changes
- Check engine light on
What to check, in order
- Read all codes across every module the tool can reach. Torque management is a conversation between modules, so the fault is often in the module at the other end.
- Check battery voltage and state of charge - a weak battery causes module communication faults with no wiring problem at all.
- Inspect the connectors at both modules.
- Ask whether a module was recently replaced or updated. A software mismatch produces exactly this and no amount of wiring diagnosis will find it.
- Check the wiring between the modules for damage.
Read this code from your own car
Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.
Where this code sits
P00xxP01xxP02xxP03xxP04xxP05xxP06xxP07xxP08xxP09xxP0AxxP0BxxP0CxxP0DxxP0ExxP0FxxP10xxP11xxP12xxP13xxP14xxP15xxP16xxP17xxP18xxP19xxP1AxxP1BxxP1CxxP1DxxP1ExxP1FxxP20xxP21xxP22xxP23xxP24xxP25xxP26xxP27xxP28xxP29xxP2AxxP2BxxP2CxxP2DxxP2ExxP2FxxP30xxP31xxP32xxP33xxP34xxP35xxP36xxP37xxP38xxP39xxP3AxxP3BxxP3CxxP3DxxP3ExxP3Fxx
Computer output circuits and control module
P2600P2601P2602P2603P2604P2605P2606P2607P2608P2609P2610P2611P2612P2613P2614P2615P2616P2617P2618P2619P2620P2621P2622P2623P2624P2625P2626P2627P2628P2629P2630P2631P2632P2633P2634P2635P2636P2637P2638P2639P2640P2641P2642P2643P2644P2645P2646P2647P2648P2649P2650P2651P2652P2653P2654P2655P2656P2657P2658P2659P2660P2661P2662P2663P2664P2665P2666P2667P2668P2669P2670P2671