U0268 on 2014-2018 Cadillac CTS: Lost Communication With Rear Object Detection Module Fixes

What's Unique About the 2014-2018 Cadillac CTS

The 2014-2018 CTS belongs to the third generation, which heavily integrated advanced driver-assistance systems (ADAS). These systems rely on a dedicated communication network called the object detection bus. The modules for this system are located in the rear bumper corners, making them highly susceptible to moisture, corrosion, and minor impact damage that can compromise wiring or the modules themselves. This location is the primary reason this code appears on these vehicles, as road salt, dirt, and water can accumulate inside the bumper cover.

Diagnostic Flowchart

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

Symptoms You May Notice

• "Service Side Detection System" or "Service Driver Assist" message on the Driver Information Center (DIC).
• Blind spot warning lights on the side mirrors are constantly on or do not light up at all.
• Rear Cross-Traffic Alert system is inoperative.
• Adaptive Cruise Control may be disabled.
• Parking assist features may be unavailable.

Most Likely Causes

1. Damaged Wiring or Connector at Rear Bumper 🔴 High Probability The side object detection modules and their wiring are located inside the rear bumper cover, an area prone to moisture, road salt, and debris, leading to corrosion and wire damage. Even minor bumper impacts can damage the harness. The wiring can also flex and break over time.
   How to confirm: Remove the rear bumper cover and visually inspect the wiring harness and connectors going to both the left and right side object detection modules for corrosion (green/white powder), chafing, or broken wires. Wiggle the connector and wiring while checking for communication to see if the fault is intermittent.
   Typical fix: Repair the damaged section of the wiring harness. If the connector is corroded, it may need to be replaced with a new pigtail connector. Common connector pigtails include ACDelco PT2260 or PT2834, but visual confirmation is required.
   Est. part cost: $20-$100 for connector pigtails or wiring repair supplies.
2. Failed Side Object Detection Module 🟡 Medium Probability Water intrusion is a common failure mode for these modules due to their location. The internal circuit board can corrode, causing a complete failure.
   How to confirm: After confirming the wiring and connector have good power (B+ at terminal 2), ground (less than 5 ohms at terminal 5), and communication signals (less than 1V at terminal 4), the module itself is the likely culprit. A professional scan tool can attempt to communicate directly with the module; a lack of response points to a failed module.
   Typical fix: Replace the failed side object detection module. The new module must be programmed and calibrated by a dealer or qualified shop using GM's Service Programming System (SPS).
   Est. part cost: $130-$200
3. Improperly Mounted Side Object Detection Module ⚪ Low Probability The modules are mounted on brackets that are heat-staked to the inside of the bumper fascia. A minor impact can break these mounts, causing the module to be misaligned or loose.
   How to confirm: With the bumper cover removed, inspect the module's mounting brackets for cracks or breaks. Lightly pull on the bracket to see if the heat-staked points have detached.
   Typical fix: If the bracket is broken, the rear bumper fascia may need to be repaired or replaced. Per TSB PIT5622B, even after the mount is repaired, the module may retain the fault in its memory. The only way to immediately clear the message is to replace and program the module for the affected side.
   Est. part cost: $50-$100 for bracket repair, potentially more for fascia replacement.

Rare But Worth Checking

• Faulty Active Safety Control Module: This is the main computer for the driver-assist systems. While it can fail, it's much less common than wiring or sensor issues. This should only be considered after all other possibilities have been exhausted.
• Scan Tool/MDI Cable Issue: GM issued TSB #PIT5441C stating that a faulty diagnostic interface cable (the one a technician uses) can sometimes cause false communication codes, including U0268. This is a diagnostic dead-end for a vehicle owner but is a known issue for technicians.

Diagnosis Steps

1. Connect a professional-grade scan tool capable of reading GM-specific codes from all modules.
2. Confirm U0268 is present in the Active Safety Control Module. Note any other communication codes.
3. Gain access to the rear bumper internals. This requires removing the rear bumper cover.
4. Locate the left and right Side Object Detection Modules in the corners of the bumper.
5. Carefully inspect the wiring harness and connectors leading to the modules for any signs of green/white corrosion, pinched wires, or physical damage.
6. If wiring looks good, use a multimeter to test for proper power and ground at the module connector. You should find battery voltage at terminal 2 and less than 5 ohms of resistance to ground at terminal 5.
7. Check the serial data circuit (terminal 4) for a short to voltage or ground. It should read less than 1V with the ignition on.
8. Inspect the module mounting brackets to ensure they are not broken or detached from the bumper fascia.
9. If power, ground, and communication lines test normal and the module is securely mounted, the module itself has likely failed.
10. Replace the suspected faulty part (wiring connector or module).
11. If a module was replaced, it must be programmed and calibrated using GM's SPS (Service Programming System) or an equivalent professional tool.
12. Clear all DTCs and perform a test drive to verify the repair and ensure the 'Service Driver Assist' message does not return.

Parts You'll Likely Need

• Side Object Sensing Alert Module (OEM #84729107) — This is the radar sensor module that fails due to water intrusion or internal faults, causing the communication loss. This part number supersedes 84690957, 84729103, and 84820654.
  Trusted brands: ACDelco, GM Genuine
  OEM price range: $130-$200
  Aftermarket price range: $90-$150
• Rear Bumper Harness Connector Pigtail (OEM #ACDelco PT2260 (Verify by visual match)) — The connector is a common point of failure due to corrosion from water and salt. Replacing the connector with a new pigtail is often necessary when the pins are damaged.
  Trusted brands: ACDelco, Dorman
  OEM price range: $30-$50
  Aftermarket price range: $15-$30

Related Codes That Often Appear With This One

• U0269 — This code is for the other side's rear object detection module ('Lost Communication With Rear Object Detection Module B'). It's common to see both codes if there is a shared wiring problem or if both modules have failed due to similar environmental conditions.
• U0232 — This is a similar code, 'Lost Communication With Side Object Detection Control Module Left'. U0268 is often used for the right-side module, so seeing one or the other simply specifies which sensor has the fault.
• B1011 — This code, 'ECU Software Error', can sometimes be set in the side detection modules, indicating an internal fault that requires module replacement and programming.

Technical Service Bulletins (TSBs) & Recalls

• PIT5441C: Mentions U0268 in a list of DTCs that can be falsely set by a faulty MDI (scan tool) cable when diagnosing the Object Detection System.
• PIT5622B: Describes how broken or misaligned module mounting brackets on the rear fascia can cause a 'Side Detection System Unavailable' message, even without DTCs. It explains that the module learns its incorrect position over time and will continue to show the error message at startup until it is replaced and reprogrammed, even if the physical

Platform-Specific Known Issues

• TSB PIT5622B notes that a 'Side Detection System Unavailable' message can appear without any DTCs if the module mounting bracket is broken or misaligned, which the module learns over time. This can be caused by a minor bumper impact that doesn't show external damage. The fix requires repairing the mount and then replacing/reprogramming the module to clear its learned 'bad position' memory immediately.
• TSB PIT5441C highlights that technicians may be misled by faulty diagnostic cables causing false communication codes for the object detection system, including U0268.

Mechanic-Grade Diagnostic Values

• Vehicle System Voltage — expected: 13.7-14.7V with engine running.. Failure: Consistently low voltage (e.g., below 13V) can cause various modules to malfunction and set communication DTCs.
• Module Connector Pin 4 (Serial Data) Voltage — expected: Less than 1V with key on, engine off.. Failure: Voltage significantly greater than 1V indicates a short to voltage on the data line, which will prevent communication.
• Module Connector Pin 5 (Ground) Resistance — expected: Less than 5 ohms to a known good chassis ground.. Failure: High resistance indicates a poor ground connection, which can cause intermittent or no operation. Check ground point G402.

Hidden / Shadow Codes Worth Checking

• U3000 / U3007: These are general control module and communication codes that may appear when trying to program a new side object detection module that is failing to initialize. (see via GM GDS2 scan tool during or after a failed SPS programming event.)

Scan Tool Commands That Help

• GDS2 (Global Diagnostic System 2): Vehicle DTC Information / Module Diagnostics — Use this to perform an all-module scan to confirm which module is logging the U0268 code (usually the Active Safety Control Module) and to see if other modules are also offline.
• SPS (Service Programming System) via Techline Connect: Side Object Detection Module Programming / Setup — This is a mandatory step after replacing a side object detection module. The function writes the vehicle's VIN to the new module and calibrates it to the network. A used module cannot be reprogrammed.

Wiring & Ground Locations

• G402 — Located on or near the left rear shock tower area.. This is a primary chassis ground point in the rear of the vehicle. A corroded or loose G402 can cause a high-resistance ground path for multiple rear-mounted electronic modules, including the object detection system, leading to intermittent communication faults.
• Rear Bumper Fascia Harness — Runs along the inside of the rear bumper cover, connecting to the modules in each corner.. This harness is the most common point of failure. It is susceptible to damage from moisture causing corrosion in connectors, and chafing against the bumper support bar or other components, leading to shorted or broken wires. A similar failure pattern is documented for front fascia harnesses in other GM vehicles (TSB PIT5487F).

"I Checked Everything" — The Actual Cause

• Wiring and connectors may test perfectly, but the 'Service Side Detection System' message persists at every startup. Per TSB PIT5622B, this can be caused by a broken or misaligned module mounting bracket on the inside of the bumper. The module learns its incorrect position over time and logs an internal, non-DTC fault. Even if the bracket is repaired, the module retains this 'bad position' memory. The only immediate fix is to replace and reprogram the module for the affected side.

OEM Part Supersession History

• 84690957, 84729103, 84820654 → 84729107 — Standard part revision and consolidation by the manufacturer.
  Heads up: No known incompatibilities, but any replacement, regardless of part number, requires mandatory SPS programming to link the module to the vehicle's VIN.