P0804
Shift/Timing Solenoid Intermittent
Powertrain Transmission Control Solenoid Control 🟡 Moderate — Fix within a week
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What This Actually Means
In plain language — no jargon

Your transmission's shift solenoid is cutting in and out intermittently, like a light switch that keeps flickering on and off. This prevents smooth gear changes and can cause unpredictable transmission behavior.

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Symptoms You May Notice
3 known symptoms for this code
Transmission shifting erratically or hesitating between gears
Check Engine Light illuminated
Possible limp mode or reduced engine performance
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Embedded Systems Insight
What the ECU/ECM is actually computing

The ECM monitors solenoid coil resistance and control signal voltage to the shift/timing solenoid. It detects intermittent opens or shorts by checking for unexpected resistance changes and signal dropout during normal operation cycles.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
Solenoid Coil Resistance 5-15 ohms (varies by solenoid type) Open circuit or resistance spikes indicating intermittent connection
Control Signal Voltage 12V when activated, 0V when deactivated Erratic voltage fluctuations or signal dropout
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Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Solenoid electrical connector
Clean the connector terminals with a wire brush and dielectric grease to eliminate corrosion causing intermittent contact.
2
Solenoid wiring harness
Inspect the wiring for cuts, fraying, or loose crimps between the ECM and solenoid; repair or resolder any damaged sections.
3
Shift/timing solenoid
Replace the solenoid if resistance testing shows open or out-of-spec values, or if cleaning and wiring inspection don't resolve the code.