Faulty or intermittent crankshaft position sensor or its wiring, giving a poor engine speed signal; Damaged wiring, corroded terminals or loose connectors in the engine speed signal circuit between the engine and transmission control units; Network (CAN) communication fault or related error between the engine and transmission control units; Low system voltage, poor earths or a weak battery causing unreliable signals; Faulty transmission control module or engine control module; Outdated control unit software where the manufacturer has issued a known correction for this fault.

P0725

Engine Speed Input Circuit.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
7: AreaTransmission
25: FaultThe specific fault in that area

What it means

P0725 is the generic SAE J2012 code for a fault in the engine speed input circuit as seen by the transmission control module. The control unit receives an engine speed signal, usually from the engine control unit over the network or a dedicated line, and it has found that signal missing, implausible or out of range. Without a reliable engine speed figure it cannot judge torque converter slip or shift quality.

Symptoms

Gearbox warning light or malfunction indicator lamp on
Gearbox stuck in a fixed gear (limp mode)
Harsh, delayed or flared gear changes
Torque converter lock-up not engaging
Rev counter erratic or not working
Poor fuel economy

Possible causes

Faulty or intermittent crankshaft position sensor or its wiring, giving a poor engine speed signallikely
Damaged wiring, corroded terminals or loose connectors in the engine speed signal circuit between the engine and transmission control unitslikely
Network (CAN) communication fault or related error between the engine and transmission control unitspossible
Low system voltage, poor earths or a weak battery causing unreliable signalspossible
Faulty transmission control module or engine control modulerare
Outdated control unit software where the manufacturer has issued a known correction for this faultrare

How to diagnose

Read all stored codes and freeze frame data, noting any engine speed, crankshaft sensor or network codes stored alongside P0725
Check the rev counter and live engine speed data on a scan tool, comparing the engine and transmission control unit values at idle and when revving
Inspect wiring, connectors and earths at the crankshaft sensor, transmission and control units for chafing, water ingress, corrosion or loose pins
Test battery condition and charging voltage, and check supply and earth voltages at the transmission control unit
Check for network communication faults and test CAN wiring for continuity and correct resistance as per the manufacturer's procedure
Test the crankshaft position sensor and its signal with a scope or multimeter against specification, as procedures vary by model and engine
Check for service bulletins or software updates relevant to the vehicle
Clear the code and road test to see whether it returns, confirming the repair

How to fix

Repair or replace damaged wiring, connectors or terminals in the engine speed signal circuit
Replace a faulty crankshaft position sensor
Repair network wiring faults or the module causing communication errors
Restore battery condition, charging output and earth connections
Apply a manufacturer software update only if an outdated calibration is a documented cause for the vehicle
Repair or replace a confirmed faulty control module, with coding or programming per the manufacturer

Can I keep driving?

Medium severity

The car can usually be driven carefully for a short time, but limp mode and harsh shifts can strain the gearbox, so get it checked soon. Avoid heavy loads and long journeys, and stop if the gearbox behaves erratically.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.