P0733 on 2005-2010 Pontiac G6: Gear 3 Incorrect Ratio Causes and Fixes

What's Unique About the 2005-2010 Pontiac G6

The Pontiac G6 used different automatic transmissions during this period, and the cause of P0733 can vary significantly between them. Most 2.4L and 3.5L models use a 4-speed automatic (4T45-E or 4T65-E) where failed shift solenoids are a common weak point. However, some 2007-2009 models were equipped with a 6-speed automatic (6T70/6T75) which has a well-documented history of a specific internal component—the 3-5-R clutch wave plate—fracturing and causing a loss of third gear, which directly triggers a P0733 code.

Symptoms You May Notice

• Check Engine Light is on
• Transmission slipping or hesitating to shift into 3rd gear
• Engine RPMs flare up during the 2-3 shift without an increase in speed
• Harsh or jerky shifting into or out of 3rd gear
• Vehicle gets 'stuck' in 2nd gear and will not shift up to 3rd
• Loss of power and poor acceleration
• Reduced fuel economy
• Sudden loss of 3rd, 5th, and Reverse gears (specific to 6-speed wave plate failure)

Most Likely Causes

1. Low or Dirty Transmission Fluid 🔴 High Probability → Shop Transmission Assembly Many owners neglect fluid changes, and these transmissions can develop leaks over time. Dirty or low fluid prevents proper hydraulic pressure needed for clutch engagement.
   How to confirm: Check the transmission fluid level and condition. On the 3.5L V6, there is no dipstick; the level must be checked via a plug on the side of the transmission case with the engine running and the vehicle level. The fluid should be bright red and not smell burnt. The 2.4L models typically have a dipstick.
   Typical fix: Perform a transmission fluid and filter change using DEXRON-VI fluid. If a leak is present, the leaking gasket or seal must be replaced.
   Est. part cost: $60-$120
2. Failed 2-3 or 3-4 Shift Solenoid 🟡 Medium Probability → Shop Transmission Valve Body The 4T45-E and 4T65-E transmissions used in most G6 models are known for shift solenoid failures. These electronic solenoids control the flow of fluid to engage the clutches, and they can wear out or get clogged with debris.
   How to confirm: A professional scan tool can command the solenoids to activate and monitor their response. Resistance can also be checked with a multimeter once the solenoid is accessed; for the 4T45-E, the resistance should be between 20-40 ohms. Often accompanied by solenoid-specific codes (e.g., P0976 for Shift Solenoid 'B' circuit low).
   Typical fix: Replace the faulty shift solenoid(s). This requires removing the transmission side cover, which can be done with the transmission in the vehicle but is labor-intensive. It is highly recommended to replace all solenoids (A, B, TCC, EPC) as a kit due to the high labor cost.
   Est. part cost: $40-$80 per solenoid, or $95-$150 for a complete kit
3. Broken 3-5-R Clutch Wave Plate (6-Speed Transmissions Only) 🔴 High Probability A known manufacturing defect covered by GM Special Coverage #14404B affects 2007-2009 G6 models with the 6T70/6T75 6-speed transmission. The wave plate fractures, sending debris through the transmission and causing a loss of 3rd, 5th, and Reverse gears.
   How to confirm: Confirm the vehicle has a 6-speed automatic (RPO code MH2 or MH6). The primary symptom is a sudden loss of 3rd and Reverse gears. Diagnosis requires transmission disassembly to visually inspect the wave plate. The special coverage was for 10 years/120,000 miles from the in-service date, so it is now expired for all vehicles.
   Typical fix: The transmission must be removed and disassembled to replace the broken wave plate and any other damaged components. This is effectively a partial or full rebuild. An updated, more robust wave plate is used for the repair.
   Est. part cost: $2000-$4000 for a professional rebuild
4. Worn Internal Clutch Pack ⚪ Low Probability At high mileage, the friction material on the 3rd gear clutch plates can wear out, causing slippage. This is a general wear-and-tear item.
   How to confirm: This is usually diagnosed after ruling out fluid and solenoid issues. Burnt, dark fluid with clutch material in the pan is a strong indicator. A pressure test may also show hydraulic leaks in the clutch circuit.
   Typical fix: Complete transmission rebuild to replace the worn clutch packs, seals, and gaskets.
   Est. part cost: $1800-$3000 for a rebuild

Rare But Worth Checking

• Faulty Transmission Control Module (TCM) or Wiring: → Shop Transmission Assembly While less common, a faulty TCM can fail to command shifts correctly, or damaged wiring can disrupt signals to the solenoids. This should be considered after mechanical and hydraulic causes are ruled out.
• Failed Input/Output Speed Sensor: A faulty speed sensor can send incorrect data to the TCM, causing it to misinterpret the gear ratio. This will usually be accompanied by a specific speed sensor trouble code (e.g., P0716, P0717, P0722).

Diagnosis Steps

1. Check the transmission fluid level and condition. Ensure it is full and not burnt or dark. For models without a dipstick (3.5L V6), this must be done via the check plug on the passenger side of the case with the engine running and vehicle level.
2. Scan the TCM for any other pending or active trouble codes. Pay close attention to codes for specific solenoids (P097x) or speed sensors (P07xx).
3. If fluid is low, top it off, clear the codes, and test drive to see if the problem returns. If the fluid is very dirty or burnt, perform a fluid and filter change.
4. If the problem persists, use a bi-directional scan tool to command the 2-3 and 3-4 shift solenoids on and off to check for response.
5. If a solenoid is suspected, drop the transmission pan/side cover to access the valve body and test the solenoid's resistance with a multimeter. For the 4T45-E, it should be 20-40 ohms. Compare the reading to the manufacturer's specification.
6. For 2007-2009 models, verify if it has the 6-speed transmission (RPO MH2/MH6). If so, and if Reverse gear is also lost, a broken wave plate is the most likely cause, requiring transmission removal and inspection.
7. If solenoids and fluid are good, perform a line pressure test to check for internal hydraulic leaks. Low pressure in the 3rd gear circuit points to worn internal seals or clutch packs.

Parts You'll Likely Need

• Automatic Transmission Fluid (DEXRON-VI) (OEM #10-9395 / 88865601 (ACDelco)) — The first and most critical step. Low or degraded fluid is the most common cause of shifting problems.
  Trusted brands: ACDelco, Valvoline, Castrol
  OEM price range: $10-$15 per quart
  Aftermarket price range: $8-$12 per quart
• A & B Shift Solenoid (4T45-E/4T65-E) (OEM #10478124 / 24229843) — These solenoids are a common failure point on the 4-speed transmissions, leading to incorrect gear engagement. It is best practice to replace them in pairs or as a full kit.
  Trusted brands: ACDelco, Rostra, Sonnax
  OEM price range: $40-$60 per solenoid
  Aftermarket price range: $20-$40 per solenoid
• 3-5-R Clutch Wave Plate (6T70/6T75) (OEM #24256729 (Updated design)) — The original wave plate was prone to fracturing. This updated part is required for the rebuild on affected 6-speed models.
  Trusted brands: ACDelco (GM Genuine)
  OEM price range: $15-$30
• Transmission Solenoid Master Kit (4T45-E) — Due to the high labor cost of accessing the solenoids, it is strongly recommended to replace all of them at once (Shift A/B, TCC, EPC, Pressure Switch).

Related Codes That Often Appear With This One

• P0731, P0732, P0734 — These codes indicate incorrect gear ratios in 1st, 2nd, and 4th gears, respectively. Seeing multiple P073x codes together often points to a systemic issue like low fluid, a clogged filter, or a failing TCM.
• P0976, P0977 — These codes relate to the performance of the 2-3 Shift Solenoid ('B') circuit. They strongly suggest the problem is electrical (wiring or the solenoid itself) related to that specific solenoid, rather than a purely mechanical clutch failure.

Technical Service Bulletins (TSBs) & Recalls

• 14404B — Special Coverage Adjustment - Transmission Clutch Wave Plate — Covers fractured 3-5-R wave plate in 6T70/6T75 transmissions, causing loss of 3rd, 5th, and Reverse gears. GM extended the warranty to 10 years or 120,000 miles. This coverage is now expired for all affected vehicles.
• 06-02-32-007G — Clunk, Knock or Rattle Noise From Front of Vehicle While Driving or Turning Over Bumps — Addresses a clunking noise from the front end, often caused by a slip/stick condition in the intermediate steering shaft. This is a common G6 issue unrelated to P0733 but relevant to overall vehicle ownership.
• 14329 — Special Coverage Adjustment - Power Steering — Addresses sudden loss of electric power steering assist. GM extended the warranty for this condition on some models to 10 years or 150,000 miles.

Platform-Specific Known Issues

• Owner Experience: 2009 G6 GT 3.5L with P0733: An owner on G6OwnersClub.com with a 2009 G6 GT (3.5L V6) reported experiencing code P0733 along with harsh shifting from 2nd to 3rd gear. After confirming the fluid level was correct, they replaced the 2-3 shift solenoid (Solenoid 'B'). The repair involved removing the driver's side wheel, axle, and transmission side cover. The owner noted the difficulty of the job but confirmed that replacing the solenoid resolved the P0733 code and the shifting issue. This is a classic example of a solenoid failure on the 4-speed automatic transmission.

Mechanic-Grade Diagnostic Values

• 4T45-E Pressure Control (PC) Solenoid Resistance — expected: 3.0 - 7.0 ohms. Failure: A reading outside of this range indicates a faulty solenoid coil.
• 4T45-E Transmission Fluid Temperature (TFT) Sensor Resistance — expected: Approximately 3500 ohms at 20°C (68°F) and 180 ohms at 100°C (212°F).. Failure: A reading of ≤ 43.19 ohms indicates a shorted sensor, triggering a fault for a temperature over 150°C.
• 4T45-E Transmission Fluid Pressure (TFP) Switch State — expected: A combination of ON/OFF signals from multiple pressure switches corresponding to the commanded gear.. Failure: An incorrect combination of switch states for the commanded gear can set codes like P1810. A faulty TFP switch is a common cause.

Hidden / Shadow Codes Worth Checking

• P1810: Transmission Fluid Pressure (TFP) Manual Valve Position Switch Malfunction. This code often points to a failing pressure switch manifold inside the 4T45-E, which can lead to incorrect gear ratio codes like P0733. (see via This code is a standard OBD-II code but is a critical companion to P0733, often revealing the root cause is the pressure switch assembly rather than a clutch or solenoid.)

Scan Tool Commands That Help

• GM Tech 2 / Professional Bidirectional Scanner: Transmission Output Controls (Solenoid Command) — To manually command the 2-3 shift solenoid on and off while monitoring transmission behavior. This helps isolate whether the fault is with the solenoid itself, the wiring, or a mechanical blockage in the valve body.
• GM Tech 2 / Professional Bidirectional Scanner: Adaptive Learn Reset — This must be performed after replacing major transmission components like solenoids, the valve body, or the entire transmission. It clears the old, learned shift timing and pressure values from the TCM, allowing it to learn the characteristics of the new parts for smooth shifting.

Wiring & Ground Locations

• TCM (Transmission Control Module) — On most G6 models, the TCM is located in the engine compartment on the driver's side, mounted to the strut tower or under the hood near the fuse block.. The TCM is the brain of the transmission. All sensor inputs and solenoid outputs run through it. A poor connection at its 49-way connector or a faulty module can directly cause P0733.
• G105 / G109 — G105 is located on the left rear of the engine, while G109 is on the left front of the engine compartment. These are primary grounds for engine and transmission components.. A loose or corroded ground at these locations can cause erratic behavior from sensors and solenoids, leading to incorrect ratio calculations and other transmission faults.
• Transmission Case Harness Connector — This is the main electrical plug on the transmission case that connects the internal components (solenoids, sensors) to the main vehicle harness and the TCM.. Corrosion or bent pins in this connector can interrupt the signal to or from the 2-3 shift solenoid or speed sensors, directly causing a P0733 code. It should be inspected after checking fluid.

Real Owner Repair Stories

• ScannerDanner Forum user (2009 Pontiac G6 with 4T45-E transmission) — Unspecified shifting issue, no check engine light.
  ❌ Tried (didn't work) A fluid and filter change was performed because the fluid was low, but the issue persisted.
  ✅ What actually fixed it The user acquired a bidirectional scan tool and found no codes and that solenoids were responding correctly. While the final fix was not posted, the diagnostic process correctly escalated from a fluid change to electronic testing, which is the proper procedure.

OEM Part Supersession History

• Unknown (Original factory-installed part) → 24254103 / 24256729 (Updated design) — The original 3-5-R wave plate in the 6T70/6T75 transmission was prone to fracturing due to stress at the teeth. The updated design is shot-peened for durability, and some aftermarket versions (like Sonnax) are toothless to eliminate the primary failure point.
  Heads up: Using a non-updated wave plate in a rebuild will likely lead to a repeat failure.
• 24226580 (For pre-2004 models) → 24217544 (For 2004+ models) — The design of the manifold pressure switch for the 4T45-E changed. Post-2004 models use a three-switch type manifold.
  Heads up: The earlier 6-switch manifold pressure switch is not compatible with 2004 and newer 4T45-E transmissions used in the G6.

Model Year Variations Within This Range

• 2007-2009: Some G6 models, particularly those with the 3.6L V6, were equipped with the 6-speed 6T70/6T75 automatic transmission. These are uniquely susceptible to the 3-5-R wave plate failure, which is not a concern on the 4-speed 4T45-E used in most 2.4L and 3.5L models.
• 2006-2010: The Transmission Control Module (TCM), part number 24256960, is specific to these years and requires VIN programming upon replacement to communicate correctly with the Engine Control Module (ECM) and other vehicle systems.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• Electric Power Steering (EPS) Failure 🔴 High — Very common, typically occurs around 70,000-100,000 miles. Can be intermittent at first. (Ref: Recall 14V252000, Special Coverage 14329)
• Leaking Sunroof Drain Tubes 🟠 Medium — Widespread issue where drain tubes disconnect from the sunroof cassette, causing water to leak into the headliner, A-pillars, and floorboards.
• Intermediate Steering Shaft Clunk 🟡 Low — A common clunking or rattling noise heard/felt in the steering wheel at low speeds, especially over bumps. (Ref: TSB 06-02-32-007G)
• Faulty VVT Solenoids (2.4L LE5) 🟠 Medium — Can cause rough running, stalling, and a check engine light. Often caused by infrequent oil changes.
• Failing Body Control Module (BCM) Connector 🟠 Medium — Can cause strange electrical issues, most notably the failure of tail lights. The fix often involves cleaning and applying special dielectric grease to the connector.
• Prematurely Worn Front Wheel Hub Bearings 🟠 Medium — Results in a loud humming or 'helicopter' noise that changes pitch when turning.

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: A complete, used 4T45-E transmission assembly from a low-mileage, rear-ended donor vehicle can be a cost-effective alternative to a professional rebuild, especially if the current transmission has high mileage and widespread internal wear. However, this is a gamble on labor costs if the used unit is faulty.

Donor-vehicle mileage cap: roughly under 80000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• Verify the donor vehicle's mileage and check for a history of regular maintenance if possible.
• Inspect the fluid from the donor transmission. It should be bright red, not dark brown or burnt-smelling.
• Ask for a short warranty (30-90 days) from the salvage yard to cover immediate failure upon installation.
• Ensure the gear ratio and bellhousing pattern match your vehicle's original transmission by providing the VIN.

OEM-only on this vehicle (don't cheap out):

• 3-5-R Wave Plate (6-speed): Use only the updated ACDelco OEM part (24256729) or a reputable aftermarket equivalent like Sonnax that specifically addresses the original design flaw.

Aftermarket brands forum-validated for this vehicle:

• Sonnax: For valve body components, updated wave plates, and solenoid kits.
• Rostra: A common aftermarket brand for shift solenoids and pressure switches.
• Superior Transmission Parts: Offers upgrade kits like the 'SURE-COOL' kit designed to improve solenoid longevity.

Brands owners have reported issues with on this vehicle:

• Unbranded, generic solenoid master kits from online marketplaces without positive forum feedback can be unreliable and lead to repeat repairs.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• P0976 — Shift Solenoid 'B' Control Circuit Low; often accompanies P0733 when a failed solenoid is the root cause of the 3rd gear ratio error.
• P0700 — A general Transmission Control System Malfunction code that often triggers alongside specific gear ratio codes like P0733.
• P0735 — Gear 5 Incorrect Ratio; frequently occurs with P0733 on 6-speed models (6T70/6T75) when the 3-5-R wave plate fractures.
• P0731 — Gear 1 Incorrect Ratio; another gear ratio code that may appear if low fluid or debris from a broken wave plate affects multiple gear circuits.

Frequently Asked Questions