How to Fix Diagnostic Code P1520

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🚨 Diagnostic Profile

Vehicle Make: Chrysler

System: Gear Indicator System (transmission range display and selector position feedback)

This profile covers faults where the instrument cluster or gear selector display shows an incorrect, flashing, or missing gear position. Common causes include a faulty transmission range sensor (TRS) or shift selector assembly, wiring or connector issues in the shift circuit, communication faults on the CAN bus network, or a transmission control module (TCM) fault. On many Chrysler, Dodge, and Jeep platforms, the TRS is integrated into the valve body and shares a multi-pin connector with other transmission sensors, so a single connector or ground fault can produce multiple symptoms. Confirm the exact year, model, engine, and transmission type (e.g., 62TE, ZF8HP, 845RE, or 9-speed 948TE) before proceeding, as wiring routing, sensor location, and relearn procedures vary significantly by platform.

🚨 Repair Difficulty Tier

Tier: [Intermediate]

Basic visual and connector inspections are accessible to a trained DIY owner. Sensor replacement, wiring repair, and network diagnostics require a scan tool with live data, a digital multimeter, and familiarity with transmission electrical systems. Transmission internal faults, TRS removal requiring valve body access, or TCM/BCM module programming should be referred to a professional technician with access to a factory-level scan tool.

🛠️ Resolution Steps

Step 1: Preliminary Inspection

  • Verify battery voltage is within specification — approximately 12.4–12.6V key-off (resting) and 13.5–14.7V with the engine running — using a digital multimeter at the battery terminals, and check for any recent battery disconnection, jump-start, or low-voltage event that could cause a loss of module learned values.
  • Check for stored diagnostic trouble codes in the TCM, BCM, and instrument cluster using a compatible scan tool (factory-level tool preferred for full Chrysler network coverage), and record any freeze frame data and U-codes present.
  • Inspect the gear selector assembly, shift cable, or electronic shifter linkage for looseness, binding, incorrect adjustment, or physical damage, depending on whether the vehicle uses a mechanical cable shifter or an electronic shift-by-wire module.
  • Inspect the transmission range sensor connector (typically located on the valve body exterior or transmission case) and the shifter assembly connector at the base of the center console for corrosion, bent pins, spread terminals, moisture intrusion, or chafed wiring.
  • Check fuses and relays related to the instrument cluster and transmission control circuits, typically located in the underhood Integrated Power Module (IPM/PDC) and the interior junction block/fuse panel, cross-referencing the fuse diagram on the underside of the respective cover for the exact circuit for the model in question.
  • Confirm the vehicle’s module software levels are current and check for any applicable Chrysler Technical Service Bulletins (TSBs) or recalls related to gear display or TRS faults for the specific VIN.

Step 2: Diagnostic Verification

  • Use a scan tool to view live data for the selected gear position (PRNDL state) and compare it to the physical shifter position while slowly cycling through all gears, noting any lag, skipped positions, or mismatches.
  • Test the transmission range sensor or park/neutral position switch signal circuits using a digital multimeter: with the key on and engine off, verify reference voltage (typically 5V) is present on the sensor supply circuit, and confirm the signal circuit voltage changes appropriately as the shifter is moved through each detent, comparing results to the factory service manual specification for the exact circuit identifiers.
  • Check continuity and resistance of the shift position circuits between the sensor, TCM, and instrument cluster, referencing the factory wiring diagram (FSM) section for the Transmission Range Sensor/PRNDL circuit specific to the VIN-decoded platform and transmission type.
  • Check for voltage drop across ground circuits and confirm grounds are clean, tight, and free of corrosion at the transmission case ground strap and the body/engine block ground junctions feeding the TCM and cluster.
  • Monitor CAN bus communication activity and check for network-related fault codes, including U-codes indicating loss of communication with the TCM, BCM, or cluster, to determine whether the issue is a local sensor/wiring fault or a network-wide communication fault.
  • Isolate the fault by substitution or signal tracing to confirm whether the sensor, wiring harness, shifter assembly, module, or cluster is responsible before replacing any component — do not replace parts on suspicion alone.

Step 3: Resolution & Reset Process

  • Repair or replace the faulty component, such as the transmission range sensor, shifter assembly, damaged harness section, or corroded connector terminals, following the applicable factory service manual procedure and torque specifications.
  • Clean all connectors with approved electrical contact cleaner and apply dielectric grease to terminals where specified by the service manual to prevent future corrosion.
  • If a module replacement or reprogramming is required, complete the procedure using a Chrysler-authorized programming tool (such as wiTECH 2.0) or an approved equivalent, and confirm the correct software calibration is installed and matched to the VIN.
  • Clear all diagnostic trouble codes and perform any required gear selector calibration, TRS relearn, or transmission adaptive reset procedure per the factory service manual for the specific transmission type.
  • Road test the vehicle through all gear positions under varying load and speed conditions, confirm the display updates correctly and without delay, and recheck for stored or pending codes after the test drive.
  • Document all multimeter readings, part numbers, software calibration IDs, and repair actions taken in the service record for future reference.

📦 Parts, Labor, and Budget Estimates

Required Components/Software:

  • Transmission range sensor or park/neutral position switch: OEM Mopar part — verify exact part number through dealer parts catalog using the VIN, as this varies by transmission type (62TE, ZF8HP, 845RE, 948TE, etc.)
  • Gear selector or electronic shifter assembly (if required): OEM Mopar part — verify exact part number through dealer parts catalog using the VIN
  • Wiring harness repair kit, pigtail connector, or replacement terminals: sourced per connector family identified in the wiring diagram (e.g., Metri-Pack or Weather Pack style terminals common to Chrysler transmission harnesses)
  • TCM, BCM, or instrument cluster software update (if required): latest available calibration verified and applied through wiTECH 2.0 or dealer-level programming
  • Scan tool requirement: wiTECH 2.0 (Chrysler factory-level diagnostic and programming tool) strongly recommended for full TCM/BCM network access and relearn procedures; a capable aftermarket bi-directional scan tool may suffice for basic live data and TRS circuit verification only

Average Component Price: Transmission range sensor: approximately $80–$260 depending on transmission type; electronic shifter assembly: approximately $150–$500; wiring repair kit/connector terminals: approximately $25–$100; TCM/BCM/cluster software update: typically $100–$250 in dealer programming fees if a physical module is not replaced, or $400–$900+ if a new module is required and programmed

Estimated Labor Hours: Diagnostic/inspection time: approximately 0.5–1.5 hours; TRS replacement: approximately 0.5–1.5 hours (longer if valve body access or fluid service is required); shifter assembly replacement: approximately 1.0–2.5 hours; wiring harness repair: approximately 1.0–2.0 hours depending on access; module programming/relearn: approximately 0.5–1.5 hours. Actual times should be confirmed against the applicable shop manual labor time guide for the specific year, model, and transmission combination.