What Does P078E Mean?
The shift timing solenoid B is exhibiting intermittent electrical behavior. The TCM has detected erratic signal patterns from this solenoid, which controls precise shift timing in the automatic transmission. Intermittent faults suggest a loose connection, frayed wire, or a solenoid that is beginning to fail internally, causing unpredictable shift quality.
Common Causes
35%
Loose or corroded connector at shift timing solenoid B
25%
Intermittent wiring harness break or chafing in solenoid circuit
20%
Shift timing solenoid B with intermittent internal failure
12%
Contaminated or degraded transmission fluid affecting solenoid operation
8%
TCM ground connection issue causing erratic solenoid control
Diagnostic Steps
1
Check freeze frame data to identify conditions (temperature, gear, RPM) when the intermittent fault occurs.
2
Wiggle-test the transmission wiring harness and solenoid B connector while monitoring live solenoid data for signal dropouts.
3
Inspect the internal transmission wiring harness at common chafe points for frayed or broken conductors.
4
Measure solenoid B resistance and compare to spec; flex the wiring during measurement to detect intermittent opens.
5
Check transmission fluid condition — dark, burnt, or debris-laden fluid can cause intermittent solenoid sticking.
6
If all electrical tests pass, monitor the solenoid with an oscilloscope to capture intermittent waveform anomalies.
Estimated Repair Cost
$150 - $850
Parts + labor, varies by vehicle and location
The shift timing solenoid B is exhibiting intermittent electrical behavior. The TCM has detected erratic signal patterns from this solenoid, which controls precise shift timing in the automatic transmission. Intermittent faults suggest a loose connection, frayed wire, or a solenoid that is beginning...
The most common cause of P078E (Shift Timing Solenoid B Intermittent) is: Loose or corroded connector at shift timing solenoid B
Typical repair costs for P078E range from $150 to $850, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The vehicle can be driven cautiously. Intermittent shift issues may cause momentary loss of power or unexpected gear changes. Avoid highway merging situations where unpredictable shifts could be dangerous. Schedule diagnosis promptly.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P078E to identify the root cause.
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Quick Info
Category
Powertrain
System
Automatic Transmission
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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