P0746 on 2012-2013 Mazda MAZDA3: Pressure Control Solenoid 'A' Causes and Fixes

What's Unique About the 2012-2013 Mazda MAZDA3

For the 2012-2013 Mazda3 with the SkyActiv-Drive 6-speed automatic transmission (model FW6A-EL), P0746 is often 🎬 Watch: A detailed overview of the Skyactiv Drive transmission system. not an isolated issue. Manufacturer Technical Service Bulletins (TSBs) show this code frequently appears with a host of other transmission-related codes, particularly P1738 (Automatic Transaxle Internal Malfunction). This strongly suggests that P0746 is a symptom of a larger internal problem, such as a failing valve body or contaminated oil pressure switches within the valve body, rather than a simple solenoid failure. A full diagnostic scan for accompanying codes is crucial before attempting any repairs.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Harsh, delayed, or erratic shifting
• Vehicle enters "limp mode" (stuck in one gear)
• Transmission slipping between gears
• Illuminated Check Engine Light or AT (Automatic Transmission) warning light
• Increased fuel consumption
• Transmission overheating
• Hesitation or clunking when engaging Drive from a stop.
• Inability to use manual shift mode, or only manual mode works.

Most Likely Causes

1. Faulty Transmission Valve Body 🔴 High Probability → Shop Transmission Valve Body As indicated by Mazda's own Technical Service Bulletins (#05-003-14-2898A, #05-003-14-2898), P0746 often accompanies codes pointing to a general internal transaxle malfunction (like P1738), for which the valve body is the primary suspect. The internal passages and switches can get clogged by contaminated fluid, leading to pressure control issues.
   How to confirm: A technician will use a professional scan tool to monitor solenoid commands vs. actual pressure readings and may perform a line pressure test. Visual inspection for contamination or sticking valves is necessary after removing the transmission pan. The presence of codes like P1738 is a strong indicator.
   Typical fix: Replacement of the entire transmission valve body with a new, pre-programmed unit. This is the most common and manufacturer-recommended repair.
   Est. part cost: $800-$1300
2. Failed Pressure Control Solenoid 'A' 🟡 Medium Probability → Shop Transmission Valve Body The solenoid itself can fail electrically or mechanically over time. However, on this platform, it's more likely that the solenoid's malfunction is a symptom of a larger valve body issue rather than an isolated failure.
   How to confirm: After accessing the valve body, the solenoid's resistance can be tested with a multimeter. A technician can also apply a 12V source to see if it actuates ('clicks').
   Typical fix: Replacement of the individual solenoid. This is often attempted but may not be a permanent fix if the root cause is contamination or wear within the valve body itself.
   Est. part cost: $80-$200
3. Low or Dirty Transmission Fluid ⚪ Low Probability → Shop Transmission Assembly While less common as the root cause, contaminated fluid can clog the small passages in the valve body and solenoids, causing them to malfunction. The SkyActiv-Drive transmission is sensitive to fluid quality and level.
   How to confirm: Check the transmission fluid level and condition via the dipstick (if equipped) or service port. The fluid should be red and clear (Mazda FZ fluid is blue, but turns dark with use), not brown, black, or smell burnt.
   Typical fix: Perform a transmission fluid and filter change. 🎬 Watch: Step-by-step guide for replacing ATF FZ fluid and filters. If the fluid is very dirty, a full flush may be recommended by a professional. This may resolve minor issues but is unlikely to fix a P0746 code if internal components are already damaged.
   Est. part cost: $50-$150
4. Wiring or Connector Issues ⚪ Low Probability Vibrations and heat can cause wiring leading to the transmission to become frayed, or connectors to become corroded or loose. The main harness connector to the transmission is a potential point of failure.
   How to confirm: Visually inspect the wiring harness going to the transmission. A multimeter can be used to check for continuity and proper voltage at the solenoid connector.
   Typical fix: Repair the damaged section of wire or replace the faulty connector.
   Est. part cost: $10-$50

Rare But Worth Checking

• Faulty Transmission Control Module (TCM) or Powertrain Control Module (PCM): → Shop Transmission Assembly This is a rare cause. The control module should only be considered after all other possibilities, including solenoids, wiring, and the valve body, have been thoroughly ruled out. On these models, the TCM is integrated with the valve body, so they are replaced as a single unit.

Diagnosis Steps

1. Check the transmission fluid level and condition. If it is low, top it off with the correct fluid type (Mazda FZ or equivalent). If it is dark, burnt, or contains debris, this indicates a likely internal mechanical problem.
2. Use an OBD-II scanner to check for any other pending or stored trouble codes. Pay close attention to the codes listed in the TSBs provided, especially P1738.
3. Inspect the transmission wiring harness and connectors for any visible damage, corrosion, or loose connections.
4. With a professional scan tool, monitor the live data stream for the pressure control solenoid. Observe the commanded state versus the actual state and monitor transmission line pressure.
5. If scan tool data is inconclusive, perform a manual transmission pressure test using a pressure gauge to verify if the hydraulic pressure is within the manufacturer's specifications.
6. If pressure is low or erratic, drop the transmission pan to access the valve body. Inspect the pan for excessive metal shavings.
7. Test the resistance of the Pressure Control Solenoid 'A' with a multimeter. Compare the reading to the OEM specification. Test for shorts to power or ground.
8. If the solenoid tests good but the problem persists, and especially if code P1738 is present, the issue is highly likely within the valve body, requiring replacement as an assembly.

Parts You'll Likely Need

• Transmission Valve Body (OEM #FZ2121100J, FZ2121100H) — This is the most probable cause on this vehicle when P0746 is present, especially if other solenoid codes or P1738 are also stored. The TCM is integrated with this part.
  Trusted brands: Mazda (OEM)
  OEM price range: $800-$1300
  Aftermarket price range: $370-$900 (Remanufactured)
• Pressure Control Solenoid — If diagnosis confirms the failure is isolated to just this solenoid, it can be replaced individually. This is less common for a permanent fix on this platform.
  Trusted brands: Bosch, Hitachi, Rostra
  OEM price range: $150-$250
  Aftermarket price range: $80-$150
• Automatic Transmission Fluid (Mazda FZ) (OEM #0000-FZ-113E-01) — Fluid must be replaced anytime the transmission pan is dropped for service. Mazda FZ is a specific low-viscosity fluid; using incorrect fluid can cause damage.
  Trusted brands: Mazda, Idemitsu, Ravenol
  OEM price range: $15-$25 per quart
  Aftermarket price range: $10-$20 per quart

Related Codes That Often Appear With This One

• P1738 — This is a Mazda-specific code for an automatic transaxle internal malfunction. Its presence with P0746 strongly points to a significant internal issue, as noted in TSB #05-003-14-2898A, and almost always confirms a faulty valve body.
• P0751, P0756, P0761, P0766, P0771 — These codes relate to other shift solenoids ('A', 'B', 'C', 'D', 'E'). When seen with P0746, it indicates a widespread problem within the valve body or its electrical supply, not just a single component failure. (Cited in TSB #05-003-14-2898A)
• P0842, P0847 — These codes relate to the transmission fluid pressure switches 'A' and 'B'. TSBs #05-002/15 and #05-005/14 directly address these codes, noting they are caused by contamination causing the switches within the valve body to stick. Their presence reinforces the valve body as the root cause.

Technical Service Bulletins (TSBs) & Recalls

• 05-003-14-2898A: Lists P0746 as a secondary DTC that can be stored along with primary transaxle malfunction codes like P1738, indicating a valve body replacement is the likely fix.
• 05-003-14-2898: An earlier version of the same bulletin, also listing P0746 as a related DTC to a larger internal issue.
• 05-002/15: Addresses related pressure switch codes caused by contamination in the valve body, reinforcing the known weakness of this component.
• 05-005/14: Also addresses stuck oil pressure switches due to contamination, covering the 2012-2014 Mazda3.

Platform-Specific Known Issues

• Mazda issued Technical S

Mechanic-Grade Diagnostic Values

• Pressure Control Solenoid 'A' (Linear) Resistance — expected: 5-7 ohms. Failure: A reading outside this range indicates a faulty solenoid coil.
• On/Off Solenoid Resistance — expected: 11-14 ohms. Failure: A reading outside this range indicates a faulty solenoid coil.
• Line Pressure at Idle (D range) — expected: 330 kPa (approx. 48 psi). Failure: Pressure significantly lower than specification can indicate a worn oil pump, internal leaks, or a stuck pressure regulator valve.
• Line Pressure at Stall Speed (D range) — expected: Refer to Mazda service manual for specific stall pressure values, as they vary.. Failure: Incorrect stall pressure points to internal hydraulic circuit problems, clutch slippage, or oil pump issues.

Scan Tool Commands That Help

• Mazda Modular Diagnostic System (M-MDS) or FORScan: Initial Learning Procedure — This procedure must be performed after replacing the valve body/TCM assembly to allow the new module to learn the hydraulic characteristics of the transmission. Failure to do so can result in poor shifting and other issues.
• Mazda Modular Diagnostic System (M-MDS): TCM Reprogramming — If a software update is available to address specific DTCs like those related to pressure switches (P0842, P0847), reprogramming the TCM may be required as part of the repair procedure outlined in service bulletins.

Wiring & Ground Locations

• Transmission Case Grounds — There are multiple ground points directly on the transmission case. One is on the top of the transmission housing under the harness, and two are on the front of the case (one large, one small).. The TCM and solenoids rely on solid ground connections. A corroded or loose ground on the transmission case can cause erratic solenoid behavior and communication issues, potentially triggering a P0746 code.
• G06 — Located at the left rear of the engine compartment.. This is a primary ground point for engine and transmission-related components. Verifying its integrity is a key step in diagnosing any electrical fault in the powertrain system.
• G07 — Located at the top rear of the engine.. This ground serves the TCM and other critical engine components. A poor connection here can lead to incorrect sensor readings and faulty module operation.

OEM Part Supersession History

• FZ21-21-100H → FZ21-21-100J — Part revision or improvement by the manufacturer. The newer part is the currently supplied service replacement.
  Heads up: FZ21-21-100J is listed as compatible with 2015+ models but is also the service replacement for the earlier part number used in 2012-2013 models.
• FZA1-21-100 → FZ21-21-100J — Part revision or consolidation.

Model Year Variations Within This Range

• 2012-2013: Mazda TSB #05-002/15 indicates different TCM software file names depending on the production date. Vehicles produced before March 31, 2013, use file PEY0-21-PS1-A, while those produced after use PE08-21-PS1-N. This is critical if a TCM reprogramming is attempted.