English-first OBD-II diagnostics Static, fast, focused lookup pages
CD CheckDTC Garage-grade fault lookup
Browse codes Try AI Diagnose
Home / Codes / P0787
DTC code page

P0787: Shift/Timing Solenoid A Circuit Low

Quick answer: The controller sees the shift/timing solenoid A circuit voltage lower than expected.

Drivers also search this fault as shift timing solenoid A circuit low, P0787 low input, solenoid A circuit low voltage.

Severity: high Family: powertrain Related paths: 9
Meaning

What P0787 usually means

P0787 is the low-voltage branch of the shift/timing solenoid A family. This is where the diagnosis should become disciplined and electrical before it becomes expensive. Low-circuit faults often come from shorts to ground, damaged wiring, internal harness problems, or a solenoid coil that is pulling the circuit down harder than it should. Drivers usually notice the same end result—harsh shifting, no upshift, or limp mode—but the repair path is different because the code is accusing the electrical side directly rather than a vague transmission behavior problem.

Fast triage

Start here before chasing parts

  • Scan first: save freeze-frame and pending codes before clearing anything.
  • Confirm the complaint: compare the stored code with current drivability symptoms.
  • Use context: trims, live data, and related codes usually narrow the fault faster than guesswork.
  • Work simplest to hardest: leaks, connectors, maintenance items, and known patterns before expensive components.
Initial checks

What to check first

  • See whether the complaint happened suddenly, because abrupt change often fits a circuit fault better than gradual hydraulic decline.
  • Inspect the case connector and harness routing for chafing or fluid migration.
  • Check whether other solenoid electrical codes are present, which can point to a shared wiring problem.
Driving risk

Can you keep driving?

P0787 often pushes the transmission into harsh-shift or backup-gear operation because the controller cannot trust the solenoid command. Limit driving if normal upshifts are gone.

High urgency: If symptoms are active, reduce driving and diagnose quickly before secondary damage builds.
Likely causes

Common causes behind this code

  • Short to ground in the shift/timing solenoid A circuit
  • Failed solenoid A coil pulling the circuit low
  • Connector corrosion, fluid intrusion, or pin damage
  • Internal transmission harness damage
  • Module driver issue or shared low-reference problem

Cause phrases often tied to this code: short to ground on shift timing solenoid A, low voltage solenoid circuit, internal harness damage, failed solenoid coil, connector corrosion.

Diagnostic order

Suggested workflow

  1. Capture freeze-frame and all related codes.
  2. Measure circuit voltage, resistance, and continuity for the shift/timing solenoid A path using service information.
  3. Inspect external and internal harness sections, pass-through connectors, and pin fit.
  4. If wiring is sound, test the solenoid coil and module control path.
  5. After repair, verify the code stays gone and the transmission exits any fail-safe strategy.
Avoid guesswork

Common mistakes

  • Jumping into valve-body work before proving the electrical fault.
  • Replacing a solenoid without checking the harness that feeds it.
  • Assuming the connector is fine because it looks clean externally.
Repair path

Practical fix guidance

  • Treat P0787 as an electrical proof problem first: circuit, connector, harness, solenoid coil, then control module.
  • If multiple solenoid low-circuit codes appear together, inspect shared power and ground paths early.
  • Only move into hydraulic diagnosis after the circuit side has been proven healthy.
Vehicle context

Affected brands in this MVP

Brand hubs help broaden internal linking now and can evolve into make-specific diagnostic notes later.

Aliases and common searches

English phrases tied to P0787

Useful when the driver knows the wording but not the exact DTC yet.

  • shift timing solenoid A circuit low
  • P0787 low input
  • solenoid A circuit low voltage
Related search intent

Queries this page can answer naturally

  • P0787 code meaning
  • what does P0787 mean
  • shift timing solenoid A circuit low
  • P0787 transmission code
FAQ

Quick questions about P0787

What does circuit low mean on P0787?

It means the controller sees the solenoid circuit voltage lower than expected, usually because of a short, coil fault, or wiring issue.

Can connector corrosion trigger P0787?

Yes. Corrosion or fluid intrusion can distort the circuit enough to set a low-voltage style fault.

Should I replace the valve body for P0787?

Not first. The correct order is to prove the circuit, connector, internal harness, and solenoid coil before mechanical teardown.