P0697 on 2021 Jeep Wrangler: Sensor Voltage Circuit Fault Causes and Fixes

What's Unique About the 2021-2021 Jeep WRANGLER

For the 2021 Jeep Wrangler (JL), a primary cause for P0697 is not a failed part, but a software sensitivity issue. A specific Technical Service Bulletin (TSB 08-029-23) was issued because the code could be falsely triggered when driving in snowy or icy conditions with the traction control system turned off. In many cases, a simple software update at the dealership resolves the problem without any parts being replaced, a fix corroborated by numerous owner experiences.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Check Engine Light is on
• Vehicle may enter 'limp mode' with reduced engine power
• Electronic Throttle Control (red lightning bolt) light may illuminate
• Erratic or harsh transmission shifting
• Malfunction or warning light for the 4WD system
• Unstable engine operation, hesitation, or surging at idle
• Inaccurate gauge readings on the instrument cluster
🎬 Watch this breakdown of P0697 symptoms, causes, and common fixes.
• Multiple warning lights appearing at once, especially in cold weather

Most Likely Causes

1. Powertrain Control Module (PCM) Software Requires Update 🔴 High Probability → Shop Engine Control Module (ECM) A specific TSB (#08-029-23) was released by the manufacturer for this exact issue on 2021 Wranglers, indicating a known software glitch that occurs when driving in 2WD on snow or ice with the Traction Control System (TCS) turned off.
   How to confirm: Contact a Jeep dealership with your Vehicle Identification Number (VIN) to verify if TSB 08-029-23 is open for your vehicle and if the software update has been performed. This should be the first step.
   Typical fix: A technician will use a diagnostic scan tool (wiTECH) to reprogram or 'reflash' the PCM with the updated software. This is typically covered under warranty.
   Est. part cost: $0
2. Wiring Harness Damage 🟡 Medium Probability Wranglers are often used off-road and are subject to modifications, which increases the risk of wiring harnesses rubbing against chassis components, melting on hot exhaust parts 🎬 See how to properly replace a melted or damaged wiring connector., or corroding from moisture exposure. The harnesses leading to the transmission and transfer case are common areas to inspect for this code.
   How to confirm: Perform a thorough visual inspection of the wiring harnesses, especially around the engine, transmission, transfer case, and firewall. Look for chafed insulation, broken wires, or corroded connectors. Pay close attention to where the harness may contact the frame or exhaust components.
   Typical fix: Repair the damaged section of the wire and protect it from future damage. This may involve soldering, using heat-shrink tubing, and re-routing or securing the harness with zip ties.
   Est. part cost: $5-$50
3. Faulty Sensor on Circuit 'C' ⚪ Low Probability Any sensor can fail, and when a sensor on the 5V reference circuit shorts internally, it can bring down the entire circuit, triggering P0697. For this code, sensors related to the transmission or driveline are common suspects.
   How to confirm: This requires a wiring diagram to identify the correct sensors on the 'C' circuit. Disconnect sensors on the suspected circuit one by one. After unplugging each sensor, clear the codes and see if P0697 returns. If the code stays away after unplugging a specific sensor, that sensor is the likely culprit.
   Typical fix: Replace the identified faulty sensor.
   Est. part cost: $50-$200
4. Faulty Powertrain Control Module (PCM) ⚪ Low Probability → Shop Engine Control Module (ECM)
   How to confirm: This is a diagnosis of exclusion. If the software is updated, and both the wiring and all related sensors have been tested and confirmed to be good, the PCM itself may be the issue.
   Typical fix: Replace and reprogram the PCM. This typically requires a professional shop or dealership.
   Est. part cost: $800-$1500

Rare But Worth Checking

• Failing Main or Auxiliary Battery:

Diagnosis Steps

1. First, check with a Jeep dealer to see if TSB #08-029-23 applies to your vehicle and if the software update has been performed. This is the most common and simplest fix for a 2021 model.
2. If the software is current, scan for any other OBD-II codes that could point to a specific sensor or system, particularly related to the transmission or transfer case.
3. Test the health of both the main and auxiliary batteries. The complex electronics on the JL are sensitive to low voltage conditions which can set erroneous codes.
4. Perform a detailed visual inspection of the engine, transmission, and differential wiring harnesses. Look for any signs of rubbing, melting, corrosion, or loose connections.
5. Using a multimeter and a vehicle-specific wiring diagram, identify a sensor on the 'C' reference circuit. With the key on and the sensor unplugged, check for a 5-volt signal at the reference wire in the connector.
6. If 5 volts are not present, there is an open or short in the wiring between the PCM and the sensor. If the voltage is significantly low, there is likely a short to ground.
7. If 5 volts are present, the wiring to that point is likely good. The issue may be a shorted sensor. Begin unplugging sensors on that circuit one by one to isolate the faulty component.
8. If all wiring and sensors test good, the final step is to consider a faulty PCM, which should be diagnosed by a professional.

Parts You'll Likely Need

• Powertrain Control Module Software Update — As per TSB 08-029-23, a software glitch is the most common cause for this code on a 2021 Wrangler.
  Trusted brands: Mopar (Dealer Service)
  OEM price range: $0-$200
  Aftermarket price range: N/A
• Engine Wiring Harness Repair — If the cause is not software, it is often a damaged wire that needs to be repaired rather than a full part replacement.
  OEM price range: N/A
  Aftermarket price range: $5-$50

Related Codes That Often Appear With This One

• P06A3-00 — This code, 'Sensor Reference Voltage 'D' Circuit/Open', is explicitly mentioned alongside P0697 in TSB 08-029-23, indicating the software issue can affect multiple reference voltage circuits.
• P0698 — This code indicates 'Sensor Reference Voltage “C” Circuit Low', pointing to a short to ground on the same circuit.
• P0699 — This code indicates 'Sensor Reference Voltage “C” Circuit High', pointing to a short to a higher voltage source on the same circuit.

Technical Service Bulletins (TSBs) & Recalls

• 08-029-23: Addresses P0697 and P06A3 setting under specific winter driving conditions (snow/ice, 2WD, TCS off), recommending a software update for the Powertrain Control Module. This is the most critical document for this specific vehicle and code.

Platform-Specific Known Issues

• TSB 08-029-23 Software Anomaly: A known software issue documented in TSB #08-029-23 can cause this code to set on 2021 Wranglers. The bulletin states: 'P0697-00 - Sensor Reference Voltage 3 Circuit...may set after driving on snow/ice in 2WD and Traction Control System (TCS) turned off.' The official fix is a powertrain control module software update performed by a dealer.
• Real-World Example: Cold Weather Failure: A 2021 Wrangler owner on jlwranglerforums.com reported their vehicle going into limp mode at 0°F, with the dash lighting up with warnings and the engine running erratically. This experience directly mirrors the conditions described in the TSB, highlighting the link between extreme cold and this specific software fault.

Mechanic-Grade Diagnostic Values

• 5-Volt Sensor Reference Voltage — expected: 4.8 V - 5.2 V. Failure: Voltage below 4.8V or above 5.2V indicates a circuit fault (open, short to ground, or short to power).
• Resistance between 5-Volt Supply and Sensor Ground circuits — expected: Above 1000 Ohms. Failure: Resistance below 1000 Ohms indicates a short between the supply and ground circuits.
• Main Ground Strap Resistance — expected: < 0.1 Ω. Failure: Higher resistance indicates a poor ground connection, which can cause floating voltages and erroneous codes.
• Transmission Valve Body Bolt Torque — expected: 105 in-lbs. Failure: Incorrect torque can lead to transmission fluid leaks or improper valve body seating if service is required for a related sensor.

Scan Tool Commands That Help

• Professional Scan Tool (e.g., wiTECH): Bi-directional control of sensor data — To request live data from sensors on the suspected circuit. If the PCM cannot receive data despite good wiring, it points towards an internal PCM issue.
• Professional Scan Tool (e.g., wiTECH): ETC RELEARN — This function must be performed after replacing the Powertrain Control Module (PCM) to recalibrate the electronic throttle control system.

Wiring & Ground Locations

• Transmission Control Module (TCM) Harness — The wiring harness that routes over the top of the transmission and connects to the module located in the passenger side wheel well.. A known failure point involves this harness falling onto the hot exhaust due to a failed plastic retaining clip, causing wires to melt and short circuit. This can directly cause P0697 and multiple other communication codes.
• G901C — Transmission Harness Ground.. This is a primary ground point for the transmission harness. A loose or corroded connection here can interrupt sensor signals and reference voltages related to the transmission, triggering P0697.
• G904A / G904B / G905A / G908A — Dash Harness Grounds, located under the dashboard.. These grounds serve the main dash harness, which communicates with the PCM. A poor ground in this area can cause a wide range of electrical issues, including reference voltage faults.
• Driver's Side Engine Bay Ground — A ground stud on the body located near the brake booster in the driver's side of the engine compartment.. This is an accessible and critical grounding point for various engine bay components. Ensuring it is clean and tight is a key step in diagnosing any electrical fault.

Real Owner Repair Stories

• jlwranglerforums.com user 'OffroadEverything' (2021 Jeep Wrangler JLURD (Diesel) with 52,xxx miles) — Vehicle threw numerous communication error messages for almost every module and had 19 stored diagnostic trouble codes.
  ❌ Tried (didn't work) The owner immediately took the vehicle to the dealership for diagnosis.
  ✅ What actually fixed it A dealership technician discovered that the Transmission Control Module (TCM) wiring harness, which runs over the transmission, had fallen onto the exhaust and melted through, causing a short circuit. The technician noted there was a TSB related to the failure of a plastic clip meant to secure this harness.

When the Usual Fixes Don't Work

• While the most common cause of P0697 on a 2021 Wrangler is the software glitch addressed by TSB 08-029-23, this is not the only cause. There are confirmed owner reports where the TSB was not the issue. In one specific case, the vehicle displayed numerous communication codes along with P0697. The root cause was found to be a physically melted transmission wiring harness that had made contact with the exhaust system. This indicates that even if the TSB is open or has been performed, a thorough inspection of the wiring harness, particularly the section routed over the transmission, is a critical diagnostic step that must not be skipped.