B0042 on 2007-2010 GMC Sierra 2500: Airbag Light Causes and Fixes

What's Unique About the 2007-2010 Gmc SIERRA 2500

The GMT900 platform, which includes the 2007-2010 Sierra, is well-known for specific airbag system vulnerabilities. GM issued a comprehensive Technical Service Bulletin (TSB #08-09-41-002H) that directly links code B0042 to failing Connector Position Assurance (CPA) retainers on airbag wiring harnesses across dozens of its models. Additionally, the front impact sensors on these trucks are mounted in a location that makes them highly susceptible to corrosion and physical damage from moisture and road salt, a frequent source of airbag system faults on this specific generation of truck.

Diagnostic Flowchart

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

Symptoms You May Notice

• Airbag warning light illuminated on the instrument cluster
• "Service Airbag" message displayed on the Driver Information Center (DIC)

Most Likely Causes

1. Loose, Damaged, or Missing Connector Position Assurance (CPA) Retainer 🔴 High Probability This is a well-documented issue covered by GM TSB #08-09-41-002H. The small plastic clips, often yellow, become brittle over time and fail to hold the electrical connector securely, causing low resistance or an intermittent connection.
   How to confirm: Visually inspect the yellow airbag connectors, particularly at the base of the steering column and behind the airbag module itself. Check if the small CPA clip is broken, loose, or missing. The TSB covers multiple connectors in the SIR system.
   Typical fix: Replace the faulty CPA retainer (GM P/N 88988974). The TSB also recommends applying dielectric grease (GM P/N 12345579) to the connector terminals to ensure a good connection and prevent future corrosion.
   Est. part cost: $5-$15
2. Faulty Clock Spring (SIR Coil) 🟡 Medium Probability The clock spring is a wear item. It contains a coiled ribbon of wires that flexes every time the steering wheel is turned, and these wires can eventually break or short out, causing resistance faults. This is a common failure point after many years and miles.
   How to confirm: After confirming connectors are good, test the clock spring circuits for continuity and resistance using a multimeter. This requires removing the steering wheel airbag and the clock spring itself. Other symptoms of a failing clock spring can include the horn or steering wheel-mounted controls (like cruise control) also failing.
   Typical fix: Replace the clock spring assembly.
   Est. part cost: $100-$150
3. Damaged Wiring Under Driver's Seat 🟡 Medium Probability Seat movement, especially with power seats, can chafe, stretch, or break the wires in the yellow airbag harness located under the seat over time. Items stored under the seat can also snag and damage the harness. Forum users on PerformanceTrucks.net have documented finding severed wires in the under-seat harness on similar GM trucks.
   How to confirm: Visually inspect the yellow-loomed wiring harness under the driver's seat for any signs of damage, pinching, or broken wires. Wiggling the harness while observing the airbag light (with the key on) can sometimes pinpoint an intermittent fault. A user on a forum found a wire broken right at the terminal pin, inside the connector, where it was not externally visible.
   Typical fix: Repair the damaged section of wire with a proper solder and heat-shrink connection. In severe cases, the harness pigtail may need to be replaced.
   Est. part cost: $5-$50

Rare But Worth Checking

• Corroded or Failed Front Impact Sensor: While a failed front impact sensor is a very common issue on these trucks, it often sets other specific codes (like B0091). However, corrosion can cause unpredictable electrical issues, including shorts that could potentially trigger a B0042. These sensors are located behind the front bumper and are prone to failure from moisture and road salt, which causes the case to crack open.
• Faulty Sensing and Diagnostic Module (SDM): Internal failure of the airbag control module is rare but possible. On some GM trucks, the SDM is located under the driver's seat and can be susceptible to moisture damage if the carpet gets wet. This should only be considered after all other components—wiring, connectors, clock spring, and sensors—have been thoroughly tested and ruled out.

Diagnosis Steps

1. SAFETY FIRST: Disconnect the negative battery terminal and wait at least 15 minutes for the airbag system's backup power to discharge before performing any physical inspection or repair.
2. Scan for Codes: Use a high-quality scan tool capable of reading SRS/airbag codes to confirm B0042 is the active code. Note any symptom bytes if available.
3. Inspect Connectors (per TSB): Visually inspect all accessible yellow airbag connectors, starting with the ones at the base of the steering column and under the driver's seat. Look for loose connections or damaged/missing CPA retainers as described in TSB #08-09-41-002H.
4. Inspect Under-Seat Wiring: Carefully examine the wiring harness under the driver's seat for any signs of chafing, pinching, or breaks.
5. Test the Clock Spring: If connectors are secure, the clock spring is the next suspect. This involves removing the driver's airbag and steering wheel to access the component for electrical testing. This step is best left to a professional.
6. Inspect Front Impact Sensors: Check the front impact sensor(s) located on the radiator support behind the grille/bumper area. Look for physical damage, swelling, or cracks, which indicate internal corrosion and failure.
🎬 Watch: How to replace a corroded front impact sensor
7. Test the SDM: If all other components test good, the final step is to test the wiring to and from the SDM and consider the module itself as the potential fault.

Parts You'll Likely Need

• Connector Position Assurance (CPA) Retainer (OEM #88988974) — This is the most common failure point identified in GM Technical Service Bulletin #08-09-41-002H for this exact code.
  Trusted brands: ACDelco / GM Genuine Parts
  OEM price range: $5-$15
  Aftermarket price range: $5-$10
• Clock Spring (OEM #25966966, 25966963, 15829095) — This is a common wear-and-tear part that contains the wiring for the driver's airbag. It fails from the repeated motion of steering. Part number varies based on options like cruise control.
  Trusted brands: ACDelco, Standard Motor Products, Dorman (e.g., 525-032)
  OEM price range: $100-$190
  Aftermarket price range: $60-$120
• Front Impact Sensor (OEM #15854647) — Though it may set other codes, this sensor is a very common failure on this truck platform due to corrosion and is a key part of the airbag system.
  Trusted brands: ACDelco, Dorman (590-203)
  OEM price range: $150-$200
  Aftermarket price range: $50-$100

Related Codes That Often Appear With This One

• B0044 — B0044 indicates 'Driver Frontal Deployment Loop Stage 2 Open/High Resistance'. Both B0042 and B0044 relate to the same circuit. A loose connector could cause either a low resistance (B0042) or open circuit (B0044) fault depending on how the terminals make contact. Both are listed in TSB #08-09-41-002H.
• B0022 — B0022 is for 'Driver Frontal Deployment Loop Stage 1 Resistance Low'. Since the Stage 1 and Stage 2 circuits are bundled together in the same clock spring and connectors, a fault in one can be related to a fault in the other. This code is also covered by the same TSB #08-09-41-002H.

Technical Service Bulletins (TSBs) & Recalls

• 08-09-41-002H: Intermittent AIR BAG Indicator/Lamp Illuminated with DTC(s) B0012, B0013, B0015, B0016, B0019, B0020, B0022, B0023, B0026, B0033, B0040, B0042 or B0044 Set (Inspect and Replace Connector Position Assurance (CPA) Retainer)

Platform-Specific Known Issues

• TSB #08-09-41-002H was issued by GM specifically for intermittent airbag lights with code B0042 (and others), identifying the primary cause as a faulty Connector Position Assurance (CPA) retainer.
• Owners on forums for GMT900 trucks frequently report solving airbag light issues by inspecting wiring under the seats, where harnesses can be damaged by seat movement or items stored on the floor.

Mechanic-Grade Diagnostic Values

• Driver Frontal Deployment Loop Stage 2 Resistance — expected: 1.3 - 4.8 ohms. Failure: A reading of less than 1.3 ohms will set DTC B0042.
• SDM Ground Circuit Resistance to Chassis — expected: Less than 0.1 Ω. Failure: Higher resistance indicates a poor ground connection at a location like G302, which can cause unpredictable module behavior.

Hidden / Shadow Codes Worth Checking

• B0042 02 or B0042 0D: This is the DTC followed by a 'symptom byte'. For B0042, '02' or '0D' specifically indicates 'Resistance Below Threshold', confirming the fault is a short or low resistance condition, not an open circuit. (see via A professional-grade scan tool like the GM Tech2 or GDS2 is required to view symptom bytes.)

Scan Tool Commands That Help

• GM Tech2 / GDS2: Clear All SIR DTCs — After a repair is completed, SIR codes are often 'latched' and cannot be cleared by disconnecting the battery or using a generic OBD-II scanner. This specific command must be sent to the SDM to turn off the airbag light.
• GM Tech2 / GDS2: Data Display > SIR > Deployment Loop Resistance — To view the live resistance value (in ohms) of the driver's airbag circuit. A technician will monitor this while wiggling harnesses or turning the steering wheel to pinpoint intermittent shorts or opens.

Wiring & Ground Locations

• Driver Airbag Connector — Behind the driver's airbag module in the steering wheel, and at the base of the steering column.. This is the primary connector for the circuit. The Stage 2 loop wires are typically Dark Green and Light Green. A poor connection here is the most common cause.
• G302 — Under the driver or passenger seat, bolted to the floor/transmission hump.. This is a primary ground point for the Sensing and Diagnostic Module (SDM). A corroded or loose ground here can cause the SDM to malfunction and set false codes.
• Under-dash Fuse Block — At the driver's side of the dashboard, accessible when the driver's door is open.. This fuse block powers the SIR system via specific fuses (e.g., Fuses 40 and 45 in the under-hood block for some models). Water intrusion from a windshield or roof leak can corrode this panel and cause airbag system faults.

Real Owner Repair Stories

• SilveradoSierra.com forum user (2008 GMC Sierra (GMT900 platform)) — Airbag light on, codes B0042 and B0044 present.
  ❌ Tried (didn't work) Replacing the CPA retainer clip per TSB #08-09-41-002H., Replacing the clock spring assembly.
  ✅ What actually fixed it Found a broken wire inside the main harness connector that plugs into the base of the clock spring. The wire had broken off the terminal pin itself and was not visible until the connector was disassembled. Repairing this wire resolved the codes.

OEM Part Supersession History

• 15829231, 25953143 → 25966966 — Part consolidation and potential design updates.
  Heads up: Part 25966966 is the widely recognized replacement for many 2007-2010 models with cruise control. Always verify fitment with VIN as steering wheel control options can change the required part.