P0720 Code: Chevrolet Malibu (2017-2023) - Causes, Symptoms & Fixes

No recalls found in NHTSA database.

Note: The real NHTSA data provided for Chevrolet Malibu (2017-2023) shows two owner complaints (P0302 and P0420) and no official recalls. There is no P0720 entry in the provided complaints. This guide uses P0720 general guidance for this vehicle range, with caveats about data limitations.

1. CODE MEANING AND SEVERITY

• What P0720 means: P0720 is the Diagnostic Trouble Code for Output Shaft Speed Sensor Circuit Malfunction. The output shaft speed (OSS) sensor monitors the rotation speed of the transmission’s output shaft and provides that data to the transmission control module (TCM) and, in some vehicles, the ECM.
• What it does: The OSS data helps the TCM coordinate shifts, torque converter lockup, and overall transmission behavior. A faulty OSS signal can cause incorrect shift timing, harsh or late shifts, or the TCM entering a fail-safe mode.
• Severity for a 2017-2023 Malibu: Moderate to potentially severe. It can cause rough or erratic shifting, gear hunting, or even limp-home behavior if the TCM cannot rely on accurate speed data. In some cases the speedometer may also read incorrectly or fail to register vehicle speed. If left unaddressed, repeated driving with this fault can stress the transmission and lead to increased wear.

2. COMMON CAUSES ON CHEVROLET MALIBU

• Faulty Output Shaft Speed Sensor (sensor itself worn or failed)
• Damaged, corroded, or unplugged OSS sensor wiring or connector (pins bent, corrosion, moisture, loose harness)
• Poor ground or bad 5-volt reference supply from the PCM/TCM to the OSS sensor
• Wiring harness chafing, rubbing, or pinched insulation near the transmission
• Faulty Transmission Control Module (TCM) or outdated software/ calibration
• Mechanical issues near the sensor (reluctor ring damage, misalignment, or transmission internal wear) affecting sensor readings
• Related fluid issues (low fluid, dirty/contaminated fluid) can sometimes impact sensor behavior indirectly or trigger related transmission codes
• Secondary codes that often accompany P0720: P0715 (input speed sensor circuit), P0716 (input sensor range/performance), P0722 (output shaft speed sensor range/performance), and occasionally P0700 (transmission control system fault) depending on the vehicle’s system wiring and software

3. SYMPTOMS

• Transmission shifting issues:
  • Harsh, delayed, or slipping shifts
  • Shifting at the wrong times or failure to upshift/downshift correctly
  • Occasional limp-home mode (limited gears)
• Speedometer issues:
  • Erratic or inoperative speedometer, since OSS data feeds vehicle speed information
• Driveability:
  • Hesitation or lack of acceleration
  • Unpredictable or inconsistent transmission behavior
• MIL/Check Engine Light:
  • P0720 (and possible related codes such as P0715, P0716, P0722) may appear
• Other symptoms to watch for:
  • Noticeable transmission flare or shudder during shifts
  • Intermittent drive complaints that match with gear changes or vehicle speed

4. DIAGNOSTIC STEPS
   Important: If you’re not comfortable performing electrical tests, consult a qualified technician. The steps below outline a practical approach and may require factory service data or a GM-compatible scan tool.

• Step 1: Retrieve and review codes

  • Use a quality OBD-II scanner capable of reading GM-specific codes and live data.
  • Note all codes (P0720 and any related codes such as P0715, P0716, P0722, P0700). Freeze-frame data can help correlate fault conditions (speed, RPM, load, temperature).

• Step 2: Visual inspection

  • Locate the OSS sensor at the transmission output area.
  • Inspect the sensor, wiring harness, and connector for damage, wear, moisture, or oil leaks.
  • Check for loose or corroded pins in the sensor connector and ensure the ground strap is intact.

• Step 3: Check wiring and connectors

  • Inspect the wiring harness for abrasion, cuts, or pinched insulation.
  • Disconnect, clean, and reseat the OSS connector; apply dielectric grease if appropriate.
  • Confirm there is no corrosion inside the connector “pins” and that the harness routing avoids heat sources or moving parts.

• Step 4: Verify power, ground, and reference signals

  • With engine off, back-probe the OSS connector to verify:
    • 5-volt reference from the PCM/TCM to the OSS sensor (power supply)
    • Ground continuity at the sensor circuit
  • Start the engine and monitor live data:
    • OSS RPM vs. engine RPM and vehicle speed (if available). The OSS should correlate logically with other speed signals; a large discrepancy or a flat line indicates a fault.
  • If the sensor is not providing a signal or shows erratic readings, suspect the OSS sensor or its wiring.

• Step 5: Sensor resistance and signal check (when guidance/specs are available)

  • Measure resistance across the OSS sensor terminals (refer to GM service data for the correct spec; typical values should be within a defined range and show continuity; infinite resistance indicates an open; very low resistance could indicate a short).
  • If you have access to an oscilloscope or a high-quality scan tool with waveform capture, observe the OSS waveform while the vehicle is running. A clean, regular waveform is expected for a functioning sensor.

• Step 6: Check for related transmission communication issues

  • Look for additional codes that indicate TCM communication or sensor range/performance issues (e.g., P0715, P0722, P0716). These can confirm a signal quality problem rather than a pure sensor fault.

• Step 7: Transmission fluid and hardware check

  • Check transmission fluid level and condition (color, smell, contamination).
  • If fluid is old, low, or contaminated, consider a transmission service per GM specs. Some issues can be exacerbated by fluid problems or sludge affecting internal sensor readings or transmission operation.

• Step 8: Firmware/software considerations

  • Some OSS-related issues respond to TCM software updates or recalibration. Check for available GM dealership/service bulletins or updates for your model year and transmission.
  • If a software fault is suspected, a dealer may perform a reflash or update.

• Step 9: Repair decision points

  • If the OSS sensor itself tests defective or the wiring/connector is severely damaged, plan for sensor replacement and wiring repair as needed.
  • If wiring is intact but the fault persists after sensor replacement, consider a TCM fault or software issue.
  • After any repair, clear codes and perform a road test to verify that the fault does not reoccur.

5. RELATED CODES

• P0715: Input/Turbine Speed Sensor Circuit
• P0716: Input/Turbine Speed Sensor Circuit Range/Performance
• P0722: Output Shaft Speed Sensor Circuit Range/Performance
• P0700: Transmission Control System Malfunction (generic)

Note: In practice, you may see multiple codes together. Prioritize addressing the P0720 fault, and use related codes to guide you toward the root cause (sensor vs wiring vs TCM/software vs mechanical issue).

6. REPAIR OPTIONS AND COSTS (2025 PRICING GUIDANCE)
   Prices vary by region, dealer vs independent shop, and exact transmission model. The Malibu can use different transmissions across years, so costs are approximate ranges.

• Output Shaft Speed Sensor replacement

  • Parts: roughly $30–$150 (OEM vs aftermarket varies)
  • Labor: about 0.5–1.5 hours
  • Typical total: $150–$500

• Wiring harness/connector repair or replacement

  • Parts: harness segments or connectors typically $20–$200
  • Labor: 1–3 hours depending on accessibility
  • Typical total: $200–$800

• Transmission fluid service (if indicated by diagnosis)

  • Parts: Dexron VI or equivalent fluid, filter if applicable
  • Labor: 1–2 hours
  • Typical total: $120–$250
  • Note: Some newer GM transmissions may not have a traditional filter service in certain service intervals; follow GM spec.

• TCM software update or reprogramming

  • Parts: minimal
  • Labor/LCMS programming: typically $120–$400 at independent shops; dealer programming may be higher
  • Typical total: $150–$600

• Transmission control module (TCM) replacement

  • Parts: $400–$900 (used or reman may be cheaper; OEM new higher)
  • Labor: 1–4 hours
  • Typical total: $800–$2,500

• Transmission replacement (last-resort scenario)

  • Parts: long-block assembly or whole transmission
  • Labor: typically 6–12+ hours
  • Typical total: $2,500–$6,500+ (depending on model and core availability)

• Summary guidance

  • Most P0720 cases resolve with OSS sensor or wiring repair and a software check.
  • If the fault persists after sensor and wiring repair, evaluate the TCM and possible software updates, and consider a more extensive transmission service.

7. DIY vs PROFESSIONAL

• DIY considerations
  • Visible wiring and connector work is within many hobbyist skill sets.
  • You can perform basic electrical checks (power, ground, continuity) with a multimeter and collection of back-probing tools.
  • A scope or advanced scan tool helps validate OSS waveform and correlation with vehicle speed – often beyond basic DIY capability.
  • Safety: working on transmissions requires disconnecting the battery and careful handling of transmission fluids and electrical connectors.
• When to seek a professional
  • If you do not have reliable diagnostic tools or you’re not comfortable with electrical testing, wiring inspection, or transmission electronics, a professional technician is recommended.
  • If the code recurs after a sensor replacement or if you suspect TCM/software issues, a GM dealer or shop with GM-specific diagnostic equipment is advised.

8. PREVENTION

• Regular transmission service
  • Use the correct Dexron VI (or GM-specified fluid) and follow GM maintenance intervals for your engine/transmission combo.
  • Change the fluid and filter per GM guidelines if applicable; contaminated or degraded fluid can affect transmission sensors and overall shift behavior.
• Protect electrical systems
  • Ensure wiring harnesses to sensors stay routed away from heat sources, moving parts, and potential water intrusion.
  • Fix fluid leaks promptly to reduce corrosion risk around connectors and the sensor.
• Monitor and address symptoms early
  • If the MIL comes on or if you notice shifting irregularities, address them promptly to avoid cascading transmission issues.
• Software updates
  • Check for factory service updates or TCM reprogramming recalls/TSBs that address OSS behavior; apply updates as recommended by GM.

Data limitations and context

• The provided NHTSA data for Chevrolet Malibu (2017-2023) includes two owner complaints (P0302 and P0420) and no recalls. P0720 is not listed in these complaints, and there are no recalls in the dataset. This guide uses general automotive knowledge about P0720 and Malibu transmission configurations to provide a practical diagnostic approach.
• Actual costs, service times, and parts availability can vary by year/model and local market. Always confirm with your repair shop or dealer for precise pricing and the exact service procedure for your specific Malibu’s transmission type.