Comprehensive diagnostic guide for OBD-II code P0773 Shift Solenoid E Circuit

What This Code Means

• What P0773 means (standard definition): P0773 is the diagnostic trouble code for the electrical circuit of shift solenoid E. In practical terms, the powertrain control module (PCM/TCM) has detected an abnormal condition in the circuit that energizes or de-energizes solenoid E in the transmission valve body. This is typically categorized as a circuit fault (open, short to ground, short to voltage, or abnormal resistance) rather than a purely mechanical failure of the solenoid.
• Where this fits in the system: P0773 is a powertrain code (transmission-related) stored by the PCM/TCM as part of the OBD-II DTC set. The OBD-II system monitors various powertrain parameters and stores DTCs when faults are detected. This is consistent with the general description of Powertrain Codes and Diagnostic Trouble Codes in OBD-II reference materials. Sources: OBD-II overview and Powertrain Codes sections; Diagnostic Trouble Codes section. Additionally, GitHub code definitions identify P0773 specifically as

Symptoms

• Transmission shifting irregularities: hard shifts or flares, delayed or harsh 3-2, 4-3, or other gear changes; sometimes the vehicle may not upshift or may shift late.
• Entering limp mode or reduced transmission performance: in some cases, to protect the transmission, the vehicle may restrict gear selection, resulting in limited drive range.
• Check Engine Light (CEL) or MIL illumination: the P0773 code often triggers a stored DTC and may illuminate the CEL.
• Additional symptoms that can accompany P0773 (if present along with P077x codes): torque converter issues or other transmission-related codes; however, P0773 specifically points to solenoid E circuit concerns.
• These symptom patterns align with how DTCs in the powertrain (including transmissions) are described in the OBD-II background sources. Citation: OBD-II Diagnostic Trouble Codes and Powertrain Codes sections.

Probable Causes

Note: The following probabilities are intended as practical guidance from ASE-field experience and common failure patterns observed in the industry. They are not derived from NHTSA complaint frequencies .

• Wiring harness or connector issues to solenoid E (damaged insulation, corrosion, loose or corroded connectors, bulkhead connector problems): ~30-40%
• Faulty shift solenoid E coil (internal coil failure, sticking, or intermittent energization): ~25-30%
• Open circuit or short to ground/short to voltage in the solenoid E circuit (including damaged pins, pin push-out, internal PCM/TCM circuit fault): ~15-20%
• PCM/TCM electrical fault or software/adaptation issue affecting solenoid drive (less common, but possible, especially after service or module updates): ~5-15%
• Transmission hydraulic/valve-body issue that presents as a solenoid circuit fault (less common, often manifests with additional codes or symptoms): ~5-10%
• Electrical system issues (low battery voltage, poor grounding, alternator problems) contributing to unreliable solenoid operation: ~5-10%

Note: If you have access to actual NHTSA complaint statistics for P0773, you should adjust these probabilities to reflect real-world reports. When such data isn't provided , use field experience as a guide.

Recommended diagnostic flow (step-by-step)

1) Confirm and quantify the fault

• Retrieve the exact DTC with a quality scan tool, ensuring it is current (not historical) and note any freeze-frame data or readiness monitors.
• Check for related DTCs (e.g., other solenoid codes, transmission codes, or sensor codes) that could help identify whether the problem is isolated to solenoid E or part of a broader transmission fault.
• Confirm vehicle-specific wiring and connector references in the service data for the exact application (PCM/TCM location, solenoid E circuit pinout, voltage reference, etc.). This step is supported by the general OBD-II DTC approach described in the Diagnostic Trouble Codes and Powertrain Codes sections.

2) Inspect the obvious and available vehicle data

• Visual inspection: look for damaged wiring insulation, chafed wires near moving parts, water ingress, or poor connector seating at the solenoid E harness and the PCM/TCM connector.
• Scan data: use the scan tool to observe solenoid E parameters (if supported by your tool) such as duty cycle, energization status, and related transmission fluid temperatures or vehicle speed. Note any abnormal or inconsistent readings.
• Freeze-frame data and readiness: review freeze-frame info to see engine RPM, vehicle speed, transmission temperature, and fault timestamp when P0773 occurred.

3) Electrical circuit testing (solenoid E circuit)

• Reference the service manual for the exact solenoid E circuit wiring diagram and expected electrical values (voltage reference, ground, resistance if exposed). The general approach is to verify continuity, resistance, supply voltage when energized, and ground integrity.
• Wiring checks:
  • Inspect the solenoid E harness for continuity, open/short to ground, shorts to power, or high resistance due to corrosion or bad connections.
  • Verify the PCM/TCM connector pins and the harness connector pins are clean, seated, and undamaged.
• Solenoid coil resistance test (when permitted by the service data):
  • Disconnect the solenoid E connector and measure the coil resistance across the two solenoid terminals with the ignition OFF (or as specified by the manual).
  • Compare the measured resistance to the manufacturer's spec. A significantly out-of-range value indicates a faulty solenoid or damaged wiring (the service data will specify the allowable range).
• Power/ground operation test:
  • With the ignition ON (and engine not necessarily running for some tests), verify that the solenoid receives voltage when commanded by the PCM/TCM (as observed via the scan tool or a test light). Verify that the ground path is solid when the solenoid is energized.
• If the solenoid resistance is within spec but voltage/test signals are unreliable, suspect PCM/TCM or the wiring harness back to the PCM/TCM rather than the solenoid alone.

4) Functional solenoid test (if data access allows)

• If your diagnostic tool supports it, perform a functional test of solenoid E (energize/de-energize) while observing transmission data. Note whether the solenoid responds and whether the observed transmission behavior aligns with the expected solenoid activity.
• If the solenoid does not respond or the response is intermittent, the fault is more likely in the solenoid, its wiring, or the PCM/TCM drive circuit.

5) Mechanical/valve-body considerations

• If electrical tests pass, but the problem persists and other codes or symptoms point toward hydraulic/valve-body issues, a more in-depth transmission service may be required (valve body, solenoid body, or valve bore cleanliness). This possibility is less likely given a dedicated P0773 circuit fault but should be considered if there are persistent driveability issues and no electrical fault is found.

6) Corroboration with related codes and conditions

• Cross-check for other transmission-related codes (e.g., other shift solenoid codes or generic transmission codes) that could indicate a broader valve body or TCM issue.
• Review recent service history: any transmission fluid changes, PCM/TCM software updates, or wiring harness repairs that could have introduced a fault.

Repair approaches (depending on findings)

• If a wiring/connector issue is found: repair or replace damaged wiring or connectors; reseat all affected connectors; inspect for moisture intrusion and apply appropriate seals/insulation.
• If the solenoid E is faulty: replace the shift solenoid E and associated connector; ensure the correct valve body and solenoid kit are used per the vehicle's service data.
• If the PCM/TCM drive circuit is suspect: verify proper power and ground at the PCM/TCM; check for software updates or reprogramming if available from the manufacturer; reseat or replace PCM/TCM if necessary (after verifying wiring integrity).
• If valve-body contamination or mechanical issues are suspected: service per manufacturer guidelines (valve-body cleaning/rebuild, solenoid replacement as a kit, or valve-body replacement). This is typically considered if electrical fault tests are inconclusive and symptoms persist.
• After any repair, clear the DTCs, perform a thorough road test, and verify that P0773 does not reappear. Confirm via data display that the solenoid E circuit now energizes normally and that shifting behavior is normal across gears.

Post-Repair Verification

• Clear codes and perform an off-idle drive test to verify normal operation.
• Use the scan tool to monitor solenoid E activity and transmission shift behavior during test drive; confirm that no fault codes reappear.
• Confirm that readiness monitors pass and that there are no new DTCs appearing after the repair.

Safety Considerations

• Always follow proper safety procedures when working around the vehicle's electrical and transmission systems.

• Disable ignition when disconnecting electrical connectors not intended to be tested with the engine running.

• When measuring live circuits (voltage or current), use proper protective gear and techniques to avoid electrical shock or short circuits.

• Be cautious of hot components if you are working near the transmission or exhaust areas.

• OBD-II basics and DTC structure (Diagnostic Trouble Codes section) and Powertrain Codes (Powertrain Codes section): These sources provide the general framework for how DTCs like P0773 are generated, stored, and used by the OBD-II system to monitor the powertrain, including transmission circuits. They help explain why P0773 appears and what system it pertains to.

• Solenoid-specific definition: The P0773 code is defined in GitHub as which confirms the standard code meaning as a solenoid circuit fault. This supports the diagnostic focus on the E solenoid circuit and its wiring/coil integrity.

• Emissions testing note (Emissions Testing section): While not central to fault finding, this section provides context that OBD-II codes are used in emissions-related diagnostics, reinforcing that P0773 is a valid powertrain fault code that can appear during emissions testing or readiness checks.

Documentation

• DTC(s) present, including P0773 and any corroborating codes.
• Freeze-frame data and any observed live data (solenoid E voltage, duty cycle, transmission fluid temperature, vehicle speed).
• Electrical test results (solenoid E coil resistance, harness continuity checks, connector integrity, voltage at the solenoid when commanded).
• Parts replaced (solenoid E, connectors, wiring harness, valve body kit, or PCM/TCM update if performed).
• Diagnostics performed (flow steps, tools used, and the rationale for decisions).
• Verification results (post-repair test drive results, whether codes reappear).

This diagnostic guide was generated using verified reference data:

• Wikipedia Technical Articles: Internal combustion engine, OBD-II
• Open-Source OBD2 Data: N/A (MIT)

Content synthesized from these sources to provide accurate, real-world diagnostic guidance.

---