P0720: How to Diagnose & Fix — Output Speed Sensor Circuit Malfunction
13 vehicles · 7 makes · $150-$6,500 repair
How to diagnose and fix P0720: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Mercedes-Benz E-Class · 2003–2012
The 722.9 7G-Tronic transmission conductor plate (internal electrical board with speed sensors) fails, causing limp mode, harsh shifting, and loss of gears. The electrical connector corrodes or the sensors crack from heat cycling.
Common Symptoms
- Transmission goes into limp mode (stuck in one gear)
- Harsh shifting between gears
How to Fix
Replace the conductor plate and both speed sensors inside the transmission. Requires dropping the transmission pan and valve body. Replace the transmission filter and fluid at the same time.
Owner tips & cautions
- TipThe conductor plate is a $150 part and 3-hour DIY job. Many shops quote $1,500+ because they don't differentiate it from a full valve body replacement.
Sources for this issue (4)
- ECU Testing: Mercedes 7G-Tronic TCM conductor plate failuremanufacturer
- MB Medic: 722.9 7G-Tronic Valve Body & Conductor Plate Must Readmedia
- UpFix: 722.9 Transmission Conductor Plate Repair Could Save $1000smanufacturer
- The Autopian: Heres What A Conductor Plate Is And Why It Kills So Many Mercedes Vehiclesmedia
Mercedes-Benz C-Class · 2005–2013
The 722.9 7G-Tronic automatic transmission develops valve body issues causing harsh or delayed shifts, particularly the 2-3 and 4-5 upshifts. The conductor plate (electrical connector inside the valve body) is also failure-prone.
Common Symptoms
- Harsh or jerky shifting
- Delayed engagement when shifting from P to D
How to Fix
Replace the valve body or have it rebuilt by a Mercedes transmission specialist. Replace the conductor plate and speed sensors at the same time. A full transmission fluid and filter service may temporarily improve symptoms.
Owner tips & cautions
- TipChange the transmission fluid and filter every 40,000 miles. Mercedes calls it a "lifetime fill" but regular service dramatically extends valve body life.
Sources for this issue (6)
- MB Medic: 722.9 7G-Tronic Valve Body & Conductor Plate Must Readmedia
- CarComplaints: Mercedes 722.9 7G-Tronic Transmission Problems Cause Lawsuitother
- UpFix: 722.9 Transmission Conductor Plate Repair Could Save $1000smanufacturer
- MB Medic: 722.9 7G Tronic Automatic Transmission Problems and Solutionsmedia
- ECU Testing: Mercedes 7G-Tronic TCM conductor plate failuremanufacturer
- Transmission Repair Cost Guide: 722.9 Valve Body Problems & Solutionsmedia
Chrysler LeBaron · 1990–1995
The LeBaron uses the Chrysler A604 (41TE) 4-speed electronically-controlled automatic transaxle. This was one of the first fully electronic automatics and its solenoid pack is the primary failure point. The solenoids develop internal leaks and electrical failures, causing erratic shifting, no-shift conditions, and limp mode (locked in 2nd gear). The transmission controller can also fail. The A604 was so problematic that Chrysler extended warranty coverage on early units.
Common Symptoms
- Transmission stuck in 2nd gear (limp mode)
- Check engine light with P0700 and P07XX codes
- Harsh or erratic shifting between all gears
- No upshift from 2nd gear
- Transmission bangs into gear from Park
How to Fix
Replace the solenoid pack assembly (located in the valve body) with an updated unit. The solenoid pack is accessible by removing the side pan. A remanufactured solenoid pack from TransGo or Rostra is $150-250. If the transmission is in limp mode, scan for codes first — many limp mode events are caused by a speed sensor or input/output shaft sensor failure rather than the solenoid pack.
What you need to diagnose it
The repair instructions explicitly call for reading stored codes. Use a scanner that can read the named code families before choosing a repair.The recommended scanner supports these code families; confirm your exact year, model and module coverage before buying.
ANCEL AD310 Classic OBD-II Scanner
Read & clear engine (P) codes
$20–$40View
As an Amazon Associate, we earn from qualifying purchases. Prices are approximate and may vary.
Reading and clearing the code is DIY work. Module replacement or reprogramming is not — most modules are VIN-programmed, so a new one does nothing until a shop codes it to your car. Check for an open recall or service bulletin before buying anything.
Sources for this issue (1)
Kia Optima · 2001–2002
Jeep Cherokee · 2014–2015
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P0720 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0720 mean?
P0720 stands for "Output Speed Sensor Circuit Malfunction." P0720 indicates a malfunction in the transmission output speed sensor circuit. The output speed sensor measures how fast the transmission's output shaft is turning, which the computer uses to calculate vehicle speed, control shift timing, and manage torque converter lockup. When the signal is missing or implausible, the transmission may shift harshly, get stuck in one gear (limp mode), or the speedometer may read incorrectly. The fault is usually in the sensor, its wiring, or the connector, though internal transmission issues can also be responsible.
What are the most common causes of P0720?
The most common causes of P0720 are: Failed output (vehicle) speed sensor, Damaged wiring, connector, or corrosion in the sensor circuit, Metal debris on the sensor tip or damaged reluctor ring, Open or short in the signal circuit, Low or contaminated transmission fluid affecting components, Poor ground or reference voltage to the sensor, Faulty transmission control module (TCM/PCM). The specific cause varies by vehicle.
How much does it cost to fix P0720?
Repair costs for P0720 range from $150 to $6,500, depending on the vehicle and root cause.
Which vehicles are affected by P0720?
Au7o has documented P0720 across 13 vehicle models from 7 manufacturers: Chrysler, Ford, Hyundai, Jeep, Kia, Mercedes-Benz, Nissan.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.