U0159 on 2014-2018 Chevrolet Silverado 1500: Park Assist Communication Failure Causes and Fixes

What's Unique About the 2014-2018 Chevrolet SILVERADO 1500

For the 2014-2018 Silverado and its platform mates, General Motors issued multiple Technical Service Bulletins (TSBs) acknowledging that a random 'Service Parking Assist' message at startup, which sets code U0159, can be caused by a software timing issue. The official fix is to reprogram the Parking Assist Control Module with an updated calibration. This makes a software update a more likely and well-documented cause on this specific truck platform compared to a random hardware failure. Another common issue is corrosion in the rear bumper harness connectors or chafing of the harness where it passes near the spare tire and frame.

Diagnostic Flowchart

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

Symptoms You May Notice

• "Service Park Assist" message displayed on the Driver Information Center (DIC), often randomly at startup.
• The parking assist system is completely inoperative.
• Audible chimes and visual sensor indicators for parking do not function.
• The park assist on/off switch LED may be disabled.

Most Likely Causes

1. Software/Calibration Issue in Parking Assist Control Module (PACM) 🔴 High Probability GM released multiple TSBs (e.g., PIT5507E, PIT5507C) specifically to address this code being set randomly at startup due to a software anomaly. The issue is described as a random concern that may disappear after an ignition cycle.
   How to confirm: A GM dealer or qualified shop can check the vehicle's service history and current module calibration against the latest available software versions in the TIS2WEB system. If the TSB applies and the update hasn't been performed, this is the most likely cause.
   Typical fix: Reprogram the Parking Assist Control Module (K41) with the updated calibration as per TSB PIT5507E.
   Est. part cost: $0 (if under warranty) - $200
2. Damaged Wiring or Poor Connection 🟡 Medium Probability The rear bumper wiring harness, which connects the PACM to the sensors, is highly exposed to road salt, moisture, and debris. Connectors for the module and sensors can fill with water and corrode. Additionally, a known chafe point exists where the main body harness passes through the frame near the spare tire, which can damage wires for multiple rear-mounted modules.
   How to confirm: Visually inspect the wiring harness and connectors leading to the PACM and each sensor in the rear bumper. Look for green/blue corrosion, chafing, or loose pins. Drop the spare tire to inspect the harness routing along the frame for pinch points. Check for power, ground, and CAN bus signals at the module connector with a multimeter.
   Typical fix: Repair the damaged section of the wiring harness or clean/replace the corroded connector. In severe cases, the entire rear bumper harness (GM Part #23406458 for some 16-19 models) may need replacement. Protect repaired areas with loom and tape.
   Est. part cost: $10-$150
3. Failed Parking Assist Control Module (PACM) ⚪ Low Probability While less common than software or wiring issues, the module itself can fail due to internal faults or water intrusion. On some GM vehicles, the module is located in a vulnerable area like under a seat or behind a rear quarter panel where water can collect.
   How to confirm: This is typically diagnosed by exclusion. If the software is up-to-date, and all wiring, power, and ground connections are verified to be good, the module itself is the likely culprit. A high-end scan tool will show the module as completely offline.
   Typical fix: Replace the Parking Assist Control Module. The new module will require programming to the vehicle's VIN.
   Est. part cost: $100-$250
4. Blown Fuse ⚪ Low Probability A power surge or a short circuit in the harness or a sensor can blow the fuse for the park assist system.
   How to confirm: Check the fuses for the park assist system. On 2014-2018 trucks, this includes fuse F29 in the left (driver's side) instrument panel fuse block and fuse F27 in the right (passenger's side) instrument panel fuse block.
   Typical fix: Replace the blown fuse. If the fuse blows again immediately, it indicates a short circuit that must be diagnosed.
   Est. part cost: $1-$5

Diagnosis Steps

1. Scan all vehicle modules for codes. Confirm that U0159 is present and note which modules are reporting the lost communication (e.g., Instrument Panel Cluster, Body Control Module).
2. Check for Technical Service Bulletins (TSBs). This is the most critical first step. TSBs PIT5507E and PIT5507C directly address U0159 caused by a software glitch.
3. If a TSB applies, have a dealer or qualified shop perform the recommended software update for the Parking Assist Control Module (PACM). Many times, this is the complete fix.
4. If no TSB applies or the update doesn't fix the issue, check the relevant fuses. For 2014-2018 models, check fuse F27 (passenger side dash) and F29 (driver side dash).
5. Perform a thorough visual inspection of the rear bumper wiring harness. Lower the spare tire for better access. Check the main connector where the bumper harness meets the body harness, and inspect the individual sensor connectors for corrosion or damage.
6. Inspect the main vehicle harness for chafing where it runs along and through the frame rails, especially above the spare tire. This is a known issue on K2XX platform trucks and SUVs.
7. If wiring appears intact, use a multimeter to verify power and ground at the Parking Assist Control Module connector. With the ignition on, check for battery voltage (typically >10V) on the power supply pin and near-zero resistance to ground on the ground pin.
8. If power and ground are good, the final step is to suspect the module itself. This is a diagnosis by exclusion after all other possibilities are eliminated.
9. Do not replace individual parking sensors for a U0159 code unless other sensor-specific codes are also present.

Parts You'll Likely Need

• Parking Assist Control Module (OEM #84444028) — This is the module that fails to communicate, setting the U0159 code. It is replaced only after software and wiring issues have been ruled out. Note: This part number may be superseded; always verify with a dealer using the vehicle's VIN.
  Trusted brands: ACDelco (Genuine GM)
  OEM price range: $150-$250
  Aftermarket price range: $100-$180
• Rear Bumper Park Assist Wiring Harness (OEM #23406458) — This harness is located in the rear bumper and is highly susceptible to corrosion and physical damage, which can break communication lines to the PACM. This part number is for 2016-2019 models; verify fitment for your specific year.
  Trusted brands: GM Genuine
  OEM price range: $90-$150
  Aftermarket price range: $50-$100

Technical Service Bulletins (TSBs) & Recalls

• PIT5507E: Unwanted or False Alerts / Park Assist off Message / Service Park Assist Message at Start up with DTC U0159
• PIT5507C: Service Park Assist Message At Start Up With DTC U0159 / False Alerts / Park Assist Off Message.
• PIT-5507: Service Park Assist Message At Start Up With DTC U0159

Platform-Specific Known Issues

• TSB PIT5507E / PIT5507C: GM identified an issue on 2014-2018 models where a 'Service Parking Assist' message may appear at startup, setting code U0159. The cause is a software anomaly, and the fix is to reprogram the Parking Assist Control Module with an updated calibration. This is the most common fix.
• Harness Chafing: The main wiring harness running along the frame above the spare tire is a common point of failure. The harness can rub against the frame or body, eventually wearing through the insulation and causing shorts or open circuits for various rear components, including the PACM.

Mechanic-Grade Diagnostic Values

• Parking Assist Control Module (PACM) Power Supply Voltage — expected: 12V (± 0.5V) with key on, engine off.. Failure: Voltage below 9V or absent can cause the module to stop communicating.
• PACM Ground Connection Resistance — expected: Near 0 Ω when measured between the ground pin at the module connector and a known good chassis ground.. Failure: Resistance greater than a few ohms indicates a poor ground, which can cause intermittent communication loss.
• Low-Speed GMLAN (CAN Bus) Voltage at PACM Connector — expected: The single data wire for the Low-Speed GMLAN should fluctuate between 0V and 5V during active communication.. Failure: A voltage that is stuck high (near 5V) or low (near 0V) indicates a short or an open circuit on the data line.

Hidden / Shadow Codes Worth Checking

• U0159 with symptom byte -04: Indicates an open or high resistance in the communication circuit. This often points to a broken wire or a disconnected/corroded connector. (see via GM GDS2 or other professional-grade scan tool that can read manufacturer-specific symptom codes.)
• U0159 with symptom byte -18: Indicates a signal performance issue. The module is on the network but its signal is erratic, incorrect, or out of expected parameters. (see via GM GDS2 or other professional-grade scan tool that can read manufacturer-specific symptom codes.)

Scan Tool Commands That Help

• GDS2 (GM Dealer Software): Module Diagnostics > Park Assist Control Module > Configuration/Reset Functions — Used after replacing the Parking Assist Control Module to program the new module to the vehicle and configure it with the correct options (RPO codes).
• GDS2 (GM Dealer Software): Vehicle DTC Information > Clear All DTCs — After a repair (like fixing a wire or updating software), this function is used to clear the U0159 code from all modules that have stored it.

Wiring & Ground Locations

• G401 — Mounted to the left rear body mount, behind the left rear tire on the frame.. This is a primary grounding point for components at the rear of the vehicle, including the tail lamps and potentially the rear bumper harness. A corroded or loose G401 can cause various electrical issues at the back of the truck, including communication failures for modules located there.
• Rear Bumper Harness Connector — Typically located on the driver's side frame rail, near the rear bumper, where the bumper harness connects to the main body harness.. This is a major failure point. It's a large connector that is exposed to road spray, salt, and debris, making it highly susceptible to water intrusion and pin corrosion, which will sever communication with the PACM.

Real Owner Repair Stories

• silveradosierra.com forum user (2015 Chevrolet Silverado) — "Service Park Assist" message on the dash and code U0159.
  ❌ Tried (didn't work) Dealer reprogrammed the module per the TSB, but the fix only lasted a few days., Replaced the Parking Assist Control Module, but the problem returned.
  ✅ What actually fixed it The user inspected the rear bumper wiring harness and found multiple corroded and broken wires inside the loom near the main connector on the frame rail. Repairing the broken wires and sealing the harness resolved the issue permanently.

OEM Part Supersession History

• 23274024 → 23406458 — Part has been updated by the manufacturer.
  Heads up: Part 23406458 is listed for 2016-2019 models with a corner step bumper and without dual rear wheels. While it may physically connect on other years, using the wrong year harness can lead to issues. Always verify the correct harness part number by VIN.

Model Year Variations Within This Range

• 2014-2016 vs 2017-2018: While the primary fuses (F27 Right IP, F29 Left IP) are largely consistent, there can be minor differences in fuse box layouts between the early (14-16) and later (17-18) models of this generation. Always refer to the fuse map on the cover of the specific vehicle's fuse box.
• 2016-2017: TSB PIT5507C notes that for 2016-2017 Silverado 1500s, new 'scalloped' sensor rings (bezels) were introduced for the front sensors. Using older, non-scalloped rings or sensors that came with them can cause false alerts, though this typically sets sensor-specific codes, not U0159.