Intermittent wiring fault or chafed harness between the solenoid and the transmission control module; Poor connection at the transmission connector or solenoid terminals (corrosion, bent or loose pins, moisture); Shift timing solenoid B with an internal intermittent fault (worn coil or sticking plunger); Contaminated, degraded, or incorrect-level transmission fluid affecting solenoid operation; Debris or valve body wear causing the solenoid to stick intermittently; Low or unstable battery or charging voltage upsetting the solenoid drive; Transmission control module internal driver fault or outdated software where a known issue exists.

P078E

Shift Timing Solenoid B Intermittent.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
7: AreaTransmission
8E: FaultThe specific fault in that area

What it means

P078E is a generic powertrain code meaning the transmission control module has detected an intermittent fault in the circuit or operation of shift timing solenoid B. The module saw the solenoid's electrical signal or its commanded response drop out or behave erratically from time to time rather than fail permanently. Which solenoid is 'B' and what it controls depends on the make, model and transmission.

Symptoms

Intermittent harsh or delayed gear changes
Occasional flare-up in revs between gears
Transmission stuck in one gear (limp mode) at times
Gearbox warning light or malfunction indicator lamp on
Poor or inconsistent fuel economy
Fault comes and goes, sometimes clearing between drives

Possible causes

Intermittent wiring fault or chafed harness between the solenoid and the transmission control modulelikely
Poor connection at the transmission connector or solenoid terminals (corrosion, bent or loose pins, moisture)likely
Shift timing solenoid B with an internal intermittent fault (worn coil or sticking plunger)likely
Contaminated, degraded, or incorrect-level transmission fluid affecting solenoid operationpossible
Debris or valve body wear causing the solenoid to stick intermittentlypossible
Low or unstable battery or charging voltage upsetting the solenoid drivepossible
Transmission control module internal driver fault or outdated software where a known issue existsrare

How to diagnose

Read all stored and pending codes and note any related solenoid, voltage or communication faults
Review freeze frame data for gear, fluid temperature, speed and battery voltage when the fault set
Check the transmission fluid level, condition and smell, following the manufacturer's procedure for that model
Inspect the transmission connector and wiring harness for damage, chafing, corrosion, moisture and pin tension
Test battery condition and charging voltage, as low voltage can trigger intermittent solenoid faults
Measure solenoid coil resistance and compare with the manufacturer's specification for that transmission
Wiggle-test the harness with a live data or circuit monitor to see whether the fault can be reproduced
Check for applicable technical service bulletins or software updates for the specific model and transmission

How to fix

Repair or replace damaged wiring and clean or renew faulty connectors and terminals
Replace shift timing solenoid B if it fails resistance or operation tests
Correct fluid level, or change fluid and filter to the specified type if contaminated or degraded
Clean or overhaul the valve body if debris or wear is causing sticking, as the model requires
Repair battery or charging system faults
Update or replace the transmission control module software or unit only where a known fault is confirmed

Can I keep driving?

Medium severity

The car can usually be driven carefully for a short time, but get it checked soon as erratic shifting or limp mode may occur and can cause further transmission wear. Avoid heavy loads or towing until it is diagnosed.

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