P0607 on 2020-2022 Cadillac CT4: BCM Performance Fault Causes and Fixes

What's Unique About the 2020-2022 Cadillac CT4

On most cars, a P0607 code points to a serious and often expensive failure of the main engine computer (ECM/PCM). However, on the GM Global B electrical architecture used in the Cadillac CT4 and its platform mates, this code is frequently triggered by a software anomaly within the Body Control Module (BCM). GM has acknowledged this issue through service bulletins, including #22-NA-044, which initially instructed technicians to perform a global battery reset and explicitly stated 'Do not replace the BCM' as engineering was investigating the software root cause. A subsequent software update became the definitive fix. Misdiagnosing this as an ECM fault would be a costly mistake.

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 illuminated on the Driver Information Center (DIC)
• Issues with HVAC (heating and air conditioning) functions
• Erratic behavior of interior or exterior lighting
• Various messages appearing on the DIC
• Potential issues with keyless entry or vehicle starting systems

Most Likely Causes

1. Body Control Module (BCM) Software Anomaly 🔴 High Probability → Shop Body Control Module This is a known issue documented by GM in TSB #22-NA-044, which affects the CT4 and numerous other GM vehicles on the Global B platform.
   How to confirm: A GM dealer or a qualified shop with access to GM service information can check the BCM's current software calibration against the latest version available in Techline Connect. The presence of TSB #22-NA-044 in the vehicle's service history is a strong indicator.
   Typical fix: Reprogram the BCM with the latest software calibration using GM's Service Programming System (SPS). 🎬 Watch: How to get started with GM SPS2 programming The TSB initially recommended clearing codes and performing a global battery reset as a first step.
   Est. part cost: $0
2. Failing Body Control Module (BCM) ⚪ Low Probability → Shop Body Control Module While less common than a software issue, the BCM can fail internally due to hardware problems. This should only be considered after software updates are performed.
   How to confirm: If reprogramming the BCM does not resolve the code, and all power/ground circuits test okay, the module itself is suspect. TSB #22-NA-044 explicitly states not to replace the BCM unless diagnostics prove it is faulty after a software update attempt.
   Typical fix: Replace the Body Control Module and program the new unit to the vehicle's VIN.
   Est. part cost: $110-$220
3. Poor Power or Ground Connection to BCM ⚪ Low Probability All modern control modules, including the BCM, are sensitive to voltage fluctuations which can cause internal performance codes. GM TSB 18-NA-161 details numerous electrical issues caused by high resistance in battery cables or poor grounds, which can trigger a variety of module-related DTCs.
   How to confirm: Perform a voltage drop test on the BCM's power and ground circuits. Check the battery and charging system to ensure they are providing stable voltage between 12.0 and 14.8 volts. Specifically, check for a poor connection at ground G218, a known issue on some GM platforms.
   Typical fix: Clean or repair corroded terminals, tighten loose connections, or repair damaged wiring.
   Est. part cost: $0-$50

Diagnosis Steps

1. Connect a professional scan tool capable of reading codes from all vehicle modules (e.g., GM GDS2).
2. Confirm that DTC P0607 is stored in the Body Control Module (BCM), not the Engine Control Module (ECM).
3. Check for GM Technical Service Bulletins related to P0607 for this vehicle, specifically #22-NA-044.
4. Follow the TSB's initial diagnostic advice: Clear all DTCs and perform a global battery reset. Allow all modules to power down completely before restarting the vehicle to see if the code returns.
5. If the code returns, use a tool like GM's Techline Connect to check the BCM's current software calibration part number against the latest version available from GM.
6. If a newer calibration is available, reprogram the BCM using the Service Programming System (SPS) and a proper programming support tool to maintain stable battery voltage. For this vehicle platform, programming must be performed with the ignition OFF.
7. If reprogramming fails or does not fix the issue, inspect the BCM's connectors for corrosion, moisture, or damage.
8. Perform a voltage drop test on the BCM's main power and ground circuits to rule out wiring issues. Per GM guidelines, voltage drop on the negative cable should not exceed 200mV and the ground circuit itself should not exceed 0.1V.
9. If all other steps fail, the BCM is likely faulty and requires replacement and programming.

Parts You'll Likely Need

• Body Control Module (BCM) (OEM #13548774) — This is the module that sets the code. It is only replaced if a software update does not fix the issue and the module is confirmed to be faulty. This part number supersedes 13521919, 13536231, 13540165, 13541804, and 13546977.
  Trusted brands: ACDelco, GM Genuine Parts
  OEM price range: $110-$220

Technical Service Bulletins (TSBs) & Recalls

• 22-NA-044: 'Check Engine MIL Illuminated in DIC Set by Body Control Module with DTC P0607' - This bulletin confirms the issue is a BCM software anomaly and initially advised against module replacement, recommending a battery reset while a software fix was developed. It applies to the CT4, CT5, Envision, Corvette, Escalade, Tahoe, Suburban, Yukon, and Yukon XL.
• PIE0672B: '...DTC P0607 Set in BCM to determine root cause.' - This is a Preliminary Information Engineering bulletin, a request from GM engineers to dealerships for data on vehicles with this specific code to help them investigate the root cause before a final repair procedure was released.
• PIT5946: A related bulletin for DTC P0606 which also points to a BCM software update as the fix and advises against replacing the BCM unnecessarily.

Platform-Specific Known Issues

• A known software anomaly in the Body Control Module (BCM) can cause DTC P0607 to set, as documented in GM TSB #22-NA-044. The primary fix is a software update, not hardware replacement.
• This issue is not unique to the CT4 and affects a wide range of GM vehicles built on the Global B platform, including the CT5, Corvette, and various SUVs.

Mechanic-Grade Diagnostic Values

• BCM Programming Supply Voltage — expected: Stable 13.4V. Failure: Fluctuations, spikes, or voltage dropping below 12.5V or exceeding 14.0V can cause programming to fail.
• BCM Ground Circuit Voltage Drop — expected: < 0.1 Volts. Failure: A reading greater than 0.1V indicates high resistance in the ground circuit that needs to be found and repaired. A reading over 0.3V is considered a definitive failure.
• Negative Battery Cable Voltage Drop (Loaded) — expected: < 200 mV. Failure: A reading above 200 mV while cranking indicates high resistance in the main battery ground cable or its connections.

Hidden / Shadow Codes Worth Checking

• U0020, U0073, U0077, U0078, U0100, U0101, U0121, U0140, U0415, etc.: While not direct sub-codes of P0607, the presence of multiple communication (U-prefix) codes alongside P0607 is a strong indicator of a foundational power or ground issue. TSB 18-NA-161 lists dozens of such codes that can be triggered by high resistance in battery cables or poor grounds (like G218), causing widespread module communication failures. (see via A full system scan with a professional tool like GM GDS2.)

Scan Tool Commands That Help

• GM GDS2 (Global Diagnostic System 2): Output Control Functions — After retrieving the P0607 code, a technician can use this function to individually command BCM-controlled outputs (e.g., 'Headlights On,' 'Door Lock'). This helps determine if the BCM hardware is capable of performing its functions, isolating the problem to either the BCM itself, the output device, or the input switch.
• GM Techline Connect (SPS2): Service Programming System (SPS) - BCM Reprogram — This is the primary fix for the software anomaly causing P0607. It updates the BCM's firmware. For the CT4's Vehicle Intelligence Platform (VIP), this procedure must be performed with the ignition turned 'OFF' to prevent errors.

Wiring & Ground Locations

• Body Control Module (BCM) — Inside the passenger cabin, typically mounted to a bracket behind the lower dashboard panel on the driver's side, adjacent to the interior fuse block.. This is the module setting the code. Physical access is required for connector inspection, voltage testing, and replacement.
• G218 — Commonly located on the left kick panel area, near the A-pillar.. This is a major body ground point. A related GM TSB (18-NA-161) identifies a poor connection at G218 as a potential cause for numerous intermittent electrical issues and module communication DTCs, which could manifest as a P0607. Checking the integrity of this ground is a critical step when diagnosing power-related module faults.

Real Owner Repair Stories

• Carfax Vehicle History Report (2022 Cadillac CT4-V Blackwing, 2,683 miles) — Not specified, but resulted in service.
  ❌ Tried (didn't work) Unknown
  ✅ What actually fixed it The 'Body computer/module' was replaced by the dealer in January 2023.

OEM Part Supersession History

• 13521919, 13536231, 13540165, 13541804, 13546977 → 13548774 — GM frequently supersedes part numbers to incorporate hardware revisions that address durability or performance issues. The long list of superseded parts for this BCM strongly suggests that multiple revisions were made to address underlying problems, likely including the one that causes P0607.

Model Year Variations Within This Range

• 2020-2022: The official GM dealer programming software changed during this period. In July 2021, GM switched from the older TIS2Web/SPS system to the new Techline Connect platform, which uses SPS2. While the function is the same (reprogramming the BCM), the software interface and access method are different, which is a key detail for independent shops.
• 2020-2022: The 2020-2022 CT4 is built on GM's Vehicle Intelligence Platform (VIP). Unlike older GM vehicles, programming modules like the BCM on this platform requires the ignition to be turned 'OFF'. Attempting to program with the ignition 'ON' can result in errors or programming failure.