P0705 on 2007-2013 GMC Sierra 1500: Transmission Range Sensor Causes and Fixes

What's Unique About the 2007-2013 GMC Sierra 1500

For the GMT900 generation of the GMC Sierra (2007-2013), the Transmission Range Sensor is mounted externally on the driver's side of the transmission. This location makes it highly susceptible to damage from road debris, water, and corrosion over time, which is a common point of failure for these trucks. While the code itself is generic, the external placement of the sensor on this platform makes it a more frequent and straightforward repair compared to vehicles where the sensor is located inside the transmission oil pan. A notable issue on these trucks is the routing of the sensor's wiring harness, which can be too close to the exhaust, leading to melted wires and short circuits that mimic a failed sensor.

Symptoms You May Notice

• Check Engine Light is on.
• Vehicle will not start, or only starts in Neutral but not Park.
• Reverse lights do not work.
• Gear indicator on the dashboard is incorrect, blank, or does not match the shifter position.
• Transmission shifts harshly or slips between gears.
• Transmission enters 'limp mode', often stuck in one gear (usually 3rd).
• Cruise control is disabled.
• Difficulty moving the gear shifter out of Park.

Most Likely Causes

1. Failed Transmission Range Sensor (Neutral Safety Switch) 🔴 High Probability → Shop Transmission Assembly The sensor is mounted on the outside of the transmission, exposing it to heat, moisture, road salt, and grime, which leads to internal corrosion and failure.
   How to confirm: Use a scan tool to monitor the TRS data while moving the shifter. If the displayed gear position does not match the actual shifter position, the sensor is likely faulty. You can also test the sensor's output voltage at the connector for each gear position using a multimeter and a wiring diagram. A common real-world test is to see if the truck starts in Neutral but not in Park; if so, the sensor or its alignment is the primary suspect.
   Typical fix: Replace the Transmission Range Sensor. This involves disconnecting the shift linkage, removing the old sensor, installing the new one, and carefully aligning it in the Neutral position before tightening. The electrical connector can be very difficult to remove due to a factory sealant and may require gentle prying, sometimes causing the old sensor's plastic to break.
   Est. part cost: $40-$100
2. Damaged Wiring or Corroded Connector 🟡 Medium Probability The wiring harness leading to the sensor is located under the truck and is susceptible to damage from road debris, heat from the exhaust manifold causing melted wires, and moisture causing corrosion in the connector pins. This is a very common point of failure on the GMT900 platform.
   How to confirm: Visually inspect the entire wiring harness from the sensor to the main loom for any breaks, melted sections, or chafing. Unplug the connector and check for green or white corrosion on the pins. Pay close attention to the section of the harness routed near the exhaust.
   Typical fix: Repair the damaged section of wire or clean the connector terminals with an electrical contact cleaner. If the connector itself is damaged, it may need to be replaced with a new pigtail. Applying dielectric grease to the connector upon reassembly can prevent future moisture intrusion.
   Est. part cost: $10-$30
3. Misadjusted Sensor or Shift Linkage ⚪ Low Probability
   How to confirm: With the key on and engine off, slowly move the gear selector. If there are dead spots where the gear indicator disappears or if the reverse lights only flicker on, the sensor's alignment may be off. Proper alignment requires placing the transmission and the sensor in the Neutral position during installation.
   Typical fix: Loosen the sensor's mounting bolts and rotate it slightly until the scan tool shows the correct gear position (Neutral) or until the vehicle starts correctly in Park and Neutral. Then, retighten the bolts to specification.
   Est. part cost: $0

Rare But Worth Checking

• Faulty Powertrain Control Module (PCM) or Transmission Control Module (TCM): → Shop Transmission Assembly This is very uncommon. Before suspecting the PCM/TCM, all other possibilities like the sensor, wiring, and adjustment must be thoroughly ruled out. This is usually indicated if other unrelated trouble codes are also present.

Diagnosis Steps

1. Connect an OBD-II scanner and confirm the P0705 code is present. Check for any other transmission-related codes, like P0700.
2. Check the transmission fluid level and condition. While not a direct cause, low or burnt fluid can indicate larger transmission problems.
3. Perform a thorough visual inspection of the Transmission Range Sensor, its connector, and the entire wiring harness on the driver's side of the transmission. Pay special attention to the area near the exhaust manifold for signs of melting, chafing, or other heat damage.
4. With the key on and engine off, use the live data function on your scan tool to monitor the gear position (PRNDL) input. Move the shifter through all gears and verify that the data on the scanner matches the shifter's position.
5. Test the vehicle's functions. Do the reverse lights work? Does the truck start in Park? Does it start in Neutral? If it starts in any other gear, the sensor has failed in a dangerous way.
6. If the sensor data is erratic or incorrect, the next step is to test the sensor's circuit. Using a digital multimeter and a vehicle-specific wiring diagram, check for correct voltage and ground at the sensor connector.
7. If wiring and power are good, the sensor itself is the most likely cause. Be prepared for the connector to be difficult to remove.
8. If the sensor has been replaced and the issue persists, re-check the sensor's alignment. It must be perfectly aligned in the Neutral position.
9. As a final, rare step, if the sensor and wiring are confirmed to be good, the issue may lie with the PCM/TCM.

Parts You'll Likely Need

• Transmission Range Sensor / Neutral Safety Switch (OEM #ACDelco 24229422 (Verify by VIN)) — This is the component that fails most frequently, triggering the P0705 code due to its exposed location and internal wear.
  Trusted brands: ACDelco, Dorman (NS-319), Standard Motor Products (SMP)
  OEM price range: $70-$120
  Aftermarket price range: $40-$80

Related Codes That Often Appear With This One

• P0700 — P0700 is a general code indicating the Transmission Control Module (TCM) has requested the Check Engine Light to be turned on. It often appears alongside more specific transmission codes like P0705 to signal a fault within the transmission control system.

Technical Service Bulletins (TSBs) & Recalls

• While no TSB is directly for the GMC Sierra P0705, GM released Preliminary Information bulletin PIP5101 for the 2013 Chevy Spark, which experienced similar symptoms (PRNDL blank, no shift, P0705). The cause was identified as a poor connection or moisture in the Park/Neutral Position (PNP) switch connector, and the recommended fix was to inspect, clean, and apply dielectric grease to the connector terminals. This guidance is relevant to the Sierra as well.

Platform-Specific Known Issues

• A user on TacomaWorld with a P0705 code traced the issue back to faulty wiring in their trailer light harness, which caused a short and triggered the code.
• On a Geo Metro forum, a user fixed their P0705 code not by replacing the sensor, but by finding and cleaning a hidden, corroded ground wire near the intake manifold.

Mechanic-Grade Diagnostic Values

• Transmission Range Switch (TRS) Power Supply Voltage (4L60-E) — expected: Battery Voltage (approx. 12.6V with key on, engine off). Failure: No voltage or significantly low voltage indicates a problem with the fuse or wiring upstream of the sensor.
• TRS Signal Circuit Logic (4L60-E) — expected: The sensor sends a unique combination of high (5V) and low (0V) signals to the PCM for each gear position across four signal wires (A, B, C, P). For example, Park might be Low-High-High-Low. A wiring diagram is required to interpret the specific combination for each gear.. Failure: If any of the signal wires show an incorrect state for a given gear selection (e.g., stuck high or low), or if the scan tool reading doesn't match the physical gear, the sensor or its wiring is faulty.

Scan Tool Commands That Help

• Tech2 / GDS2: Transmission Data Display > PRNDL Status — This is the primary function for diagnosing P0705. It allows the technician to view the gear position being reported by the TRS to the TCM in real-time. While shifting the lever, the display should instantly match the selected gear. Any lag, incorrect reading, or blank status points directly to a fault in the TRS circuit.

Wiring & Ground Locations

• G103 / G105 — G103 is typically located on the rear of the driver's side cylinder head. G105 is often on the front of the passenger side cylinder head or engine block. Exact locations can vary slightly by engine type.. These are the main engine-to-chassis grounds. The TCM/PCM and their sensor circuits rely on these grounds for a stable reference. A loose or corroded G103 or G105 can cause erratic voltage, intermittent sensor readings, and seemingly unrelated transmission codes, including P0705.
• TRS Connector (C107 on some diagrams) — On the driver's side of the 4L60-E transmission, connected to the external Transmission Range Sensor.. This is the main failure point for wiring issues. It's exposed to road grime, moisture, and heat from the nearby exhaust. The pins can corrode, and the wires leading to it can melt or break, causing an open or short in the circuit that triggers P0705.

Real Owner Repair Stories

• Edmunds Forums user 'byancey' (2004 GMC (similar GMT800 platform, issue is relevant)) — Transmission started in 3rd gear intermittently, going into 'limp-home' mode.
  ❌ Tried (didn't work) Initial mechanic tests, Transmission fluid and filter change
  ✅ What actually fixed it The problem was a faulty ignition switch (the electrical part, not the key tumbler). It was failing to supply a steady 12V to the transmission electronics, causing the limp mode. The old switch showed carbon on the contacts. The fix was a $30 switch and $20 in labor.

OEM Part Supersession History

• 24229422 → 24298931 — Standard part lifecycle update by GM.
  Heads up: The new part number (24298931) is a direct replacement for the old one (24229422) for 4L60-E/4L80-E applications. No known incompatibilities exist. It is critical to verify this part is for the 4-speed transmission, as it will not work on 6-speed models.

Model Year Variations Within This Range

• 2007-2013: The diagnostic path for P0705 is completely different depending on the transmission. Trucks with the 4-speed automatic (4L60-E) use the external, bolt-on Transmission Range Sensor (ACDelco 24229422) discussed in the main article. However, trucks equipped with the 6-speed automatic (6L80) have the range sensor function integrated into the Transmission Electro-Hydraulic Control Module (TEHCM), which is located inside the transmission oil pan, bolted to the valve body. A P0705 on a 6-speed truck is NOT an external sensor issue; it indicates a failure of the internal TEHCM, which is a much more involved and costly repair requiring removal of the transmission pan and valve body.

Diagnostic Flowchart

Other Known Issues on This Vehicle

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

• Active Fuel Management (AFM) Lifter Failure 🔴 High — Very common, especially on 5.3L V8 engines (LC9, LMG, LY5). Can occur at any mileage but becomes more prevalent after 70,000 miles. Often presents as a ticking noise and a P0300 (random misfire) code. (Ref: Multiple TSBs exist, including 15-06-01-002F, which details diagnosis and replacement of lifters and potentially the camshaft.)
• Cracked Dashboard 🟠 Medium — Extremely common across the entire GMT900 lineup. Cracks typically appear on the driver's side above the instrument cluster and on the passenger side near the airbag. This is considered a cosmetic flaw by GM and is not covered by a recall.
• Rear Wheel Well and Cab Corner Rust 🔴 High — A chronic issue, particularly in regions that use road salt. Rust forms where the outer bedside meets the inner wheelhouse, often bubbling from the inside out. Can become a structural problem if left untreated.
• Excessive Oil Consumption 🟠 Medium — Often related to the AFM system, many owners of the 5.3L V8 report consuming 1-2 quarts of oil between changes. GM has addressed this with TSBs related to piston rings and valve covers. (Ref: Multiple TSBs exist.)
• Intermediate Steering Shaft Clunk 🟡 Low — A common complaint is a clunking or popping noise from the steering column during low-speed turns, such as in parking lots. This is due to wear in the intermediate steering shaft.

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: For trucks with the 4-speed (4L60-E) transmission, a used external Transmission Range Sensor from a junkyard can be a cost-effective option, as it is a simple, self-contained electrical switch.

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

What to inspect on the donor part:

• Inspect the connector for any signs of corrosion, broken plastic, or bent pins.
• Ensure the manual lever arm moves smoothly without binding or excessive play.
• If possible, choose a part from a vehicle in a dry, non-rust-belt climate.
• Check for an intact O-ring on the shaft to prevent future water intrusion.

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

• For 6-speed (6L80) models, if the TEHCM (internal range sensor) has failed, using a new OEM or professionally remanufactured unit is highly recommended due to the complexity of the part and the labor involved to replace it. A used TEHCM may have programming/VIN lock issues.

Aftermarket brands forum-validated for this vehicle:

• ACDelco (OEM)
• Standard Motor Products (SMP)

Brands owners have reported issues with on this vehicle:

• Some owners report premature failure or alignment issues with lower-cost, unbranded aftermarket sensors. While Dorman is a common alternative, some forum users prefer to spend slightly more for ACDelco or SMP for better longevity.

Real Owner Stories

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

Related OBD-II Codes

• P0700 — A general transmission control system malfunction code that often appears alongside P0705 when the TCM detects a range sensor issue.
• P0300 — A random misfire code associated with Active Fuel Management (AFM) lifter failure, another known high-severity issue for this vehicle platform.

Frequently Asked Questions