U0268 on 2013-2018 Cadillac ATS: Lost Communication With Side Object Sensor Fixes

What's Unique About the 2013-2018 Cadillac ATS

On the Cadillac ATS and its GM Alpha platform mates (like the Chevy Camaro and Cadillac CTS), the side object detection modules are located in the rear corners of the vehicle, inside the bumper fascia. This placement makes them highly susceptible to damage from moisture, road salt, and minor rear-end impacts. Water intrusion leading to corrosion of the module's internal board and connector pins is the single most common reason for these modules to fail, often causing this specific communication code.

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 "Side Blind Zone System Unavailable" message on the Driver Information Center (DIC).
• Amber warning lights in the side mirrors do not illuminate when a vehicle is in the blind spot.
• Amber warning lights in the side mirrors may stay on constantly or flash randomly.
• Rear Cross-Traffic Alert system is inoperative.
• In some cases, especially if the module is shorting the communication bus, other seemingly unrelated electrical issues may occur.

Most Likely Causes

1. Failed Side Blind Zone Alert (SBZA) Module 🔴 High Probability The modules are located inside the rear bumper cover, where they are vulnerable to water intrusion and corrosion over time. The seals on the module case can fail, allowing moisture to destroy the circuit board.
   How to confirm: After removing the rear bumper cover, inspect the module and its electrical connector for signs of water damage, such as green or white corrosion on the pins or a swollen module case. If power and ground are present at the connector but the module won't communicate (and wiring is good), it has failed.
   Typical fix: Replace the failed module and its connector if corroded. The new module must be programmed by a dealer or a qualified shop with GM diagnostic software (SPS).
   Est. part cost: $200-$450
2. Damaged Wiring or Connector 🟡 Medium Probability The wiring harness is also located in the vulnerable rear bumper area and can be damaged by moisture, debris, or minor collisions. The connector pins are particularly susceptible to corrosion from water wicking past the module's seal.
   How to confirm: Visually inspect the wiring harness leading to the affected module for any breaks, chafing, or corrosion. Pay close attention to the pins inside the connector. Check for stable power, ground, and communication signals at the connector with a multimeter.
   Typical fix: Repair the damaged section of the wiring harness or replace the connector pigtail. It is highly recommended to replace the pigtail if any corrosion is present to prevent a repeat failure.
   Est. part cost: $25-$100
3. Improper Module Mounting ⚪ Low Probability The modules are mounted on brackets that are heat-staked to the bumper fascia. A minor impact can break these mounts, causing the sensor to be misaligned. Per TSB PIT5622B, even a slight misalignment can cause the module to disable itself over time as it learns it cannot see objects correctly, which may not initially set a DTC.
   How to confirm: Inspect the module's mounting bracket for cracks or breaks. The module should be securely fastened and properly aligned. Lightly pull on the bracket to see if the heat stakes have detached. A misaligned module can cause the "Side Detection System Unavailable" message at every startup.
   Typical fix: Repair or replace the mounting bracket. In some cases, the entire rear fascia may need replacement if the mounting points are integral and broken. Per TSB PIT5622B, after fixing the mount, the only way to immediately clear the fault is to replace and program the module, as it takes a long time for it to 're-learn' its correct position.
   Est. part cost: $50-$150 for brackets, potentially more for fascia repair/replacement.

Rare But Worth Checking

• Faulty Diagnostic Tool (MDI Cable): GM issued TSB #PIT5441C which states that a faulty diagnostic interface cable (MDI) used by a technician can sometimes generate false U-codes, including U0268. This is a diagnostic issue for the mechanic, not a vehicle fault, but it can lead to misdiagnosis if not considered.

Diagnosis Steps

1. Scan all vehicle modules with a high-quality scan tool capable of communicating with the Active Safety Module (e.g., GM GDS2).
2. Confirm which side object sensor is not communicating (U0268 often corresponds to one side, U0269 to the other). Note the specific module that is offline.
3. Gain access to the side object sensors by removing the rear bumper cover. This typically involves removing screws in the wheel wells, under the bumper, and clips/bolts near the taillights.
4. Visually inspect the non-communicating module and its electrical connector for corrosion, water damage, or physical damage. Look for a swollen plastic case on the module or green/white powder on the connector pins.
5. If no damage is visible, use a multimeter to test for battery voltage and a solid ground at the module's connector. The Low Speed GMLAN serial data wire (typically Green) should also be checked for voltage and continuity.
6. Check the integrity of the CAN bus communication wires between the module and the Active Safety Control Module. Check for proper resistance (typically 60 ohms across the two CAN wires with the battery disconnected, if it's a terminated bus).
7. If power, ground, and wiring are confirmed to be good, the side object sensor module is the most likely culprit.
8. After replacing the module, it must be programmed and configured using GM's Service Programming System (SPS) or equivalent diagnostic software.

Parts You'll Likely Need

• Side Blind Zone Alert Sensor (OEM #84612459 (Supersedes: 22960642, 22902467, 20968741, 84512065)) — This is the module that most commonly fails due to water intrusion, causing the U0268 code. Note that left and right modules are typically the same part.
  Trusted brands: ACDelco (GM Genuine), Dorman
  OEM price range: $250-$450
  Aftermarket price range: $150-$250
• Sensor Connector Pigtail (OEM #ACDelco PT2971 (or equivalent, e.g., 13343443)) — If the original connector is corroded from water damage, it must be replaced along with the sensor module to ensure a lasting repair. Splicing in a new pigtail is standard practice.
  Trusted brands: ACDelco, Connector Experts (CE8031-3)
  OEM price range: $40-$70
  Aftermarket price range: $20-$40

Related Codes That Often Appear With This One

• U0269 — This code is for 'Lost Communication With Side Object Sensor B' (the opposite side). It's common to see both codes if there is a shared power, ground, or communication bus issue affecting both modules.
• U0075 — This code indicates a general communication bus issue on the object detection network. It can appear alongside U0268 if the problem is with the network wiring itself rather than just a single module.
• B101D — This is a general Electronic Control Unit (ECU) hardware performance code. It is often stored in the Active Safety Module alongside the U0268 code when the side object sensor has an internal failure.

Technical Service Bulletins (TSBs) & Recalls

• PIT5441C: Mentions U0268 in a list of object detection system codes and advises technicians to check their diagnostic equipment, as a faulty MDI cable can induce false communication codes.
• PIT5622B: Describes a condition where a misaligned or broken module mounting bracket can cause a 'Side Detection System Unavailable' message at startup, even without setting a DTC. It notes that after fixing the mount, the module must be replaced and programmed to clear the message immediately.

Platform-Specific Known Issues

• GM issued Special Coverage Adjustment N172097060 for some models, extending the warranty for failed Side Blind Zone Alert modules due to the known water intrusion problem. This covered the 2013-2016 Chevy Cruze, 2014-2015 Chevy Impala, and 2013-2017 GMC Acadia for 6 years or 80,000 miles. While the Cadillac ATS was not explicitly listed, the issue is identical, and owners outside the coverage window often face expensive repairs for the same design flaw.

Mechanic-Grade Diagnostic Values

• Low-Speed GMLAN Bus Resistance — expected: ~60 Ohms. Failure: A reading of ~120 Ohms indicates one of the two terminating resistors (or the wiring to it) is offline. A reading significantly less than 60 Ohms suggests a short circuit between the CAN wires.
• Low-Speed GMLAN (CAN Low) Voltage to Ground — expected: ~2.0V - 2.5V (Key On). Failure: Voltage significantly different from this range can indicate a short to power or ground on the data line.
• Low-Speed GMLAN (CAN High) Voltage to Ground — expected: ~2.5V - 3.0V (Key On). Failure: Voltage significantly different from this range can indicate a short to power or ground on the data line.
• Module Power Supply at Connector — expected: Battery Positive Voltage (typically 12V+). Failure: Low or no voltage indicates a problem with the fuse, wiring, or Rear Body Fuse Block.
• Module Ground at Connector — expected: Near 0 Ohms resistance to chassis ground.. Failure: High resistance (more than a few ohms) indicates a poor ground connection at G401, causing communication issues.

Scan Tool Commands That Help

• GM GDS2 (Global Diagnostic System 2): Module Diagnostics > Side Object Sensor Module > Configuration/Reset Functions > Side Object Sensor Module Setup — This function is required after replacing a side object sensor module. It programs the new module to the vehicle's VIN and calibrates it for operation. Without this step, a new module will not function.
• GM GDS2 (Global Diagnostic System 2): Vehicle DTC Information — Used as the first step to query all modules on the vehicle's networks. This will confirm which module(s) are not communicating and display any related DTCs from other modules, such as the Active Safety Control Module.

Wiring & Ground Locations

• G401 — Near the battery well, in the trunk/luggage compartment area.. This is the primary ground point for both the left and right side object sensor modules. A loose or corroded G401 can cause intermittent or total loss of communication for both sensors, potentially setting U0268 and U0269.
• Active Safety Control Module — Varies slightly by year and trim, but typically located in the front of the vehicle, sometimes near the front camera or under the dash. Part number 23497732 is listed for the ATS.. This is the master control unit that communicates with the side object sensors. While failure is less common than the sensors themselves, a fault within this module can also cause communication loss codes.
• Rear Body Fuse Block — Located in the left side of the luggage compartment.. This fuse block supplies power to the side object sensor modules via the 'SBZA/LDW/EOCM' fuse (typically 15A). A blown fuse or issue at this block will cut power to the sensors.
• X415 (Module Connector) — The 8-pin electrical connector at each side object sensor module in the rear bumper fascia.. This is the most common point of failure due to water intrusion. Key pins are Pin 1 (Battery Positive Voltage), Pin 5 (Ground), and Pin 6/7 (Low Speed GMLAN Serial Data).

OEM Part Supersession History

• 23453703 → 23497732 — This is the part number for the Active Safety Control Module, which governs the side sensors. The update reflects a hardware revision.
  Heads up: Using the older part number may result in software incompatibility or missing features compared to the updated module.

Model Year Variations Within This Range

• 2013-2018 (Sedan vs. Coupe): The pinout location for the Low Speed GMLAN serial data wires at the main body connectors (X500/X600) differs between the Sedan and Coupe models. On the Sedan, it is Pin 7, while on the Coupe, it is Pin 15. This is critical information for anyone tracing the wiring harness from the front to the back of the vehicle.