OBD-II trouble code
P0766: Shift Solenoid "D" Performance or Stuck Off
SAE J2012: shift solenoid D performance or stuck off. Identify D in this unit's catalog before you order. ATRA bulletin 794 shows that Ford and Mazda letters on the shared 4F27E/FN4A-EL family do not line up: Ford SSA is Mazda SSD, and Ford SSC is Mazda SSA. D is not 'the overdrive solenoid.'
Quick facts
- System
- Powertrain
- Category
- Transmission / Shift Control
- Severity
- High severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $300 – $900 (simple shift solenoid replacement)
- DIY difficulty
- Advanced DIY
One of 42 shift solenoid codes
P0766 sits in a grid: one axis is which solenoid the letter refers to, the other is what went wrong with it. Each cell is a genuinely different fault with its own diagnosis — but codes from the same row or column often appear together, and what a pairing means is usually the fastest way in. The hub page lays out all 42 and explains how to read them against each other.
See all shift solenoid codes →Browse every code in P0700–P0799, or start from the full code library.
What does P0766 mean?
Solenoid D fails this test when the result the controller commanded does not show up in the ratio, the slip, or the pressure switch this calibration watches. The letter is a slot in that controller's list. Transmission Digest notes that the same P07xx number is not interpreted the same way on every calibration. Ordering 'solenoid D' from a different maker's chart is how the wrong clutch gets replaced.
The Ford and Mazda split is the concrete case. ATRA bulletin 794 says Ford SSA on the 4F27E is Mazda SSD, and Ford SSC is Mazda SSA. A part labeled SSD in a Mazda catalog is not the Ford solenoid D. Write down the clutch from the chart that matches the brand of the controller in the vehicle, then match the part number. Higher gears are not solenoid D's property. Some charts use D in a low gear. Some do not have a D at all. If the service information has no solenoid D, you are in the wrong chart or the code has been reported by a different module.
P0768 is the electrical code for solenoid D. Separate them with the resistance test in this section. A performance code with a coil that will not measure in range is an electrical fault that the performance monitor also noticed. Replace from the electrical diagnosis, not from the gear you think D controls.
Common causes
- A case connector pin for D that is corroded, wet, or pushed back
- A parts order taken from a chart whose letters do not match this controller
- Fluid level wrong for this procedure's temperature and engine state
- Solenoid D not applying the clutch on its own row, after the letter is confirmed and the coil is in range
- A speed signal bad enough to falsify the ratio
- An open or a short in D's wire, which is P0768's job when that code is stored
Symptoms
- The clutch on solenoid D's row slips or does not apply
- A part that was replaced and the code still set, because the letter came from the other brand's chart
- P0768 stored beside P0766
- Failsafe from this calibration
- No complaint in the gears this chart does not assign to D
- A ratio error with a shift the driver may not have felt
Diagnostic steps
- 1.Open the application chart for this brand and this transmission. Find the row labeled D, or the manufacturer's name for that slot. If you are holding a Ford chart against a Mazda controller on a 4F27E/FN4A-EL, stop and use ATRA 794's letter map before you buy anything.
- 2.Confirm the vehicle actually has the solenoid this code names. A chart with no D means the code definition you are using is for a different unit.
- 3.Record commanded gear, D's command, and the ratio. The gears that slip should be the ones on D's row. Gears off that row send you to line pressure or to a speed sensor, the same fork as solenoid C.
- 4.Fluid level by this procedure. Then ignition off, case connector, coil resistance for D against this spec. P0768 changes the order: the circuit test comes before a clutch diagnosis.
- 5.Pan off, when the chart reaches it, on a lift or stands with the fluid cool. Match the part number to the confirmed letter. A pack is a catalog decision, not the default.
- 6.Verify by recording the gear on D's row. A passenger reads the ratio. The code is cleared only after that gear applies.
Repair cost
$300 – $900 (simple shift solenoid replacement)
The pair matches AutoZone's simple solenoid replacement, $300–$900 parts and labor, and only after the letter is confirmed. The wrong letter, Ford against Mazda on the 4F27E family, spends that money on a solenoid the code did not name. A rebuild is the article's separate $1,800–$3,500 band. RepairPal's fluid average of $294–$356, updated 3 September 2026, is the fill that goes with an open pan, not a second repair price stacked on the solenoid.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with transmission shift solenoid replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an advanced DIY job. It typically requires specialty tools, scan-tool access, lifting equipment, or careful sequencing to avoid causing new failures. Plan for extended downtime and have a backup vehicle. Most owners are better served by a shop that has done this repair before.