What Does P0787 Mean?
The TCM has detected that the Shift Timing Solenoid A circuit voltage or current is below the expected threshold. A low signal typically indicates an open circuit, high resistance in the wiring, or a solenoid coil that has developed excessive resistance. The solenoid may be weakly energizing or not energizing at all, preventing proper shift timing control.
Common Causes
30%
Shift timing solenoid A with high internal coil resistance or partial open
25%
High resistance in the wiring harness due to corrosion or damaged wire
25%
Corroded or damaged connector pins causing high resistance connection
12%
Poor ground connection reducing circuit current flow
8%
TCM driver circuit providing insufficient output voltage
Diagnostic Steps
1
Measure shift timing solenoid A resistance at the transmission connector — a reading significantly higher than spec indicates a failing coil.
2
Check voltage at the solenoid connector while commanded on — compare to battery voltage to identify excessive voltage drop in the circuit.
3
Inspect the transmission connector for corrosion, green or white deposits on pins, moisture intrusion, or compromised seals.
4
Perform a voltage drop test across each connection point in the solenoid circuit to isolate the source of high resistance.
5
Check the ground circuit for the solenoid — measure voltage drop between the solenoid ground pin and battery negative.
6
If all wiring tests good but voltage is still low at the solenoid, test the TCM output driver for the timing solenoid circuit.
Estimated Repair Cost
$150 - $800
Parts + labor, varies by vehicle and location
The TCM has detected that the Shift Timing Solenoid A circuit voltage or current is below the expected threshold. A low signal typically indicates an open circuit, high resistance in the wiring, or a solenoid coil that has developed excessive resistance. The solenoid may be weakly energizing or not ...
The most common cause of P0787 (Shift Timing Solenoid A Low) is: Shift timing solenoid A with high internal coil resistance or partial open
Typical repair costs for P0787 range from $150 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The vehicle is drivable but shift timing will be impaired, potentially causing delayed or poorly coordinated shifts. The condition may worsen as the high-resistance connection degrades further. Repair within a reasonable timeframe.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0787 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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