2005-2008 Acura RL SH-AWD Control Module: Solving the Warning Light
This guide explains why the 'Check SH-AWD System' light is often not the module's fault and what to do when it is.
- A replacement SH-AWD module is NOT plug-and-play; it MUST be initialized by a dealer or a qualified shop with a professional scan tool to function.
- The 'Check SH-AWD System' light is frequently caused by other issues, most commonly a weak battery, failing alternator, or an emissions system fault.
- There are no new aftermarket or remanufactured modules available, making warrantied used OEM parts the only cost-effective replacement option.
- Specific diagnostic codes starting with 44, 46, or 59 are strong indicators of an internal module failure.
Symptoms of a Failing SH-AWD Control Module
The most obvious symptom is the 'Check SH-AWD System' warning message appearing on the multi-information display. This is almost always accompanied by the SH-AWD indicator light on the instrument cluster. When this occurs, the system defaults to front-wheel drive (FWD) only, and you will notice the real-time torque distribution graphic shows no power going to the rear wheels.
However, it is critical to understand that many other issues can trigger the SH-AWD warning light as a failsafe. Acura designed the system to disable itself if it receives conflicting data or if another major vehicle system, particularly the emissions or charging system, reports a fault. Before suspecting the module itself, consider these far more common culprits:
- Weak Battery or Failing Alternator: The SH-AWD system's electromagnetic clutches require stable voltage. A weak or old battery, corroded terminals, or a failing alternator can cause voltage drops that trigger the SH-AWD light. This is one of the most frequently reported causes by owners.
- Faulty Oxygen (O2) Sensors: A failing O2 sensor will trigger a Check Engine Light and an emissions system code. Because the engine is not running optimally, the main computer often commands the SH-AWD system to shut down as a precaution.
- Loose Gas Cap: A simple loose or faulty gas cap can cause an evaporative emissions (EVAP) system leak, which turns on the Check Engine Light and, in turn, can disable the SH-AWD system.
- Other Engine or Sensor Faults: Problems with the EGR valve, purge control solenoid, or other engine sensors can all lead to the SH-AWD light coming on.
OBD-II Codes Associated with the SH-AWD System
A generic OBD-II scanner may not be able to read the specific codes from the SH-AWD module. You will likely need a professional-grade scanner (like a dealer's Honda HDS or a high-end Autel/Snap-on tool) to communicate with the module directly. When scanned, the codes can point toward the module itself or another part of the system.
| Code Prefix | Potential Meaning | Indicates Module Failure? |
|---|---|---|
| 44-xx | Power or ground circuit problem to the control module | Very Likely |
| 46-xx | Internal power source failure in the control module | Very Likely |
| 59-xx | Control unit power supply monitor problem | Very Likely |
| 41-xx | Communication error with another module (F-CAN error) | Unlikely (More likely a wiring or network issue) |
| 12, 14, 16, 19, 27, 33, 35 | Fault with an external sensor (Yaw, Steering Angle, etc.) | No (Indicates a sensor problem) |
| 52, 53, 56, 57, 81, 82 | Fault with the rear differential clutch coils or sensors | No (Indicates a differential problem) |
| 76-xx | Rear differential fluid is overheating | No (Indicates a fluid/cooling issue) |
If your diagnostic scan reveals codes starting with 44, 46, or 59, it is a strong indication that the SH-AWD control module itself has failed internally.
Known Issues, Recalls, and TSBs
There have been no recalls issued by the NHTSA for the SH-AWD control module on the 2005-2008 Acura RL. The numerous recalls for this vehicle pertain to Takata airbag inflators and a power steering hose. Likewise, there are no specific Technical Service Bulletins (TSBs) from Acura addressing a common failure pattern for this module. This suggests that module failure is not a widespread manufacturing defect but rather an uncommon, isolated component failure.
Warning: A replacement SH-AWD Control Module must be initialized to the vehicle using a compatible diagnostic tool. It is not a plug-and-play part. The system will not function until this procedure is completed.
Buying a Used SH-AWD Control Module
Given that a new OEM module costs over $1,200, a used OEM module is the only practical and cost-effective solution for most owners. There are no known new aftermarket or remanufactured modules available for this specific vehicle.
When shopping for a used module, here’s what you need to know:
- Part Number Compatibility: The OEM part numbers for this module have been updated over the years. All part numbers beginning with 48310-RJC-Axx are fully interchangeable for the 2005-2008 RL. The latest version is 48310-RJC-A09, which supersedes all earlier numbers like A02, A05, A08, etc. You can safely purchase any of these versions.
- Physical Inspection: The module is an electronic component, so there is little to inspect visually. Check for any signs of physical damage, corrosion on the pins, or evidence of water intrusion, but most failures will be internal.
- Source and Warranty: Purchase from a reputable auto recycler that offers a warranty. This protects you in the rare case that you receive a defective unit.
- Factor in Programming Costs: Remember that you will need to pay a dealership or a qualified independent mechanic to perform the initialization procedure after installation. Factor this cost into your budget.
Cost Comparison
The cost savings of buying a used module are significant.
| Part Source | Estimated Cost |
|---|---|
| New OEM | $1,250 - $1,400 |
| Used OEM | $40 - $100 |
| New Aftermarket / Remanufactured | Not Available |
| Shop Labor (Installation & Programming) | $150 - $250 |
Replacement Overview
The SH-AWD control module is located in the trunk, behind the rear seatback. The replacement process is straightforward for a DIY mechanic with basic tools.
- Disconnect the vehicle's battery.
- Access the trunk and remove the trim panels necessary to get to the area behind the rear seat.
- The module is typically mounted to a bracket. Unplug the electrical connectors.
- Unbolt the module from its mounting bracket and remove it.
- Install the replacement module, reconnect the electrical connectors, and reassemble the trunk trim.
- Reconnect the battery.
- Crucially, the vehicle must then be taken to a dealer or shop for the initialization procedure.
Frequently Asked Questions (FAQ)
Does a replacement SH-AWD module have to be programmed?
Yes, absolutely. A replacement module, whether new or used, must be 'initialized' to the vehicle's VIN and other systems using a professional-grade scan tool. The SH-AWD system will not work until this is done.
Can an independent mechanic program the module, or do I have to go to the dealer?
While the dealership can always perform the initialization with their Honda HDS tool, many professional independent auto repair shops with high-end scanners (like Autel or Snap-on) can also perform this function. It is not a function that can be done without a specialized tool.
Can I still drive my RL with the SH-AWD light on?
Yes, but with limitations. When the light is on, the car operates in front-wheel drive (FWD) only. While the car is safe to drive for normal commuting, you will not have the benefit of all-wheel drive traction on slippery surfaces or the enhanced handling the system provides. It is recommended to diagnose and fix the underlying issue promptly.
My SH-AWD light is on. Does that mean my control module is bad?
Not necessarily. In fact, it's more likely that the light is on due to another problem. The most common causes are a weak battery, failing alternator, or a fault in the emissions system (like a bad oxygen sensor or loose gas cap). Always diagnose these simpler, more common issues before replacing the expensive control module.
Technical Specifications
OEM Part Numbers: 48310-RJC-A02 48310-RJC-A03 48310-RJC-A05 48310-RJC-A06 48310-RJC-A07 48310-RJC-A08 48310-RJC-A09
Location: In trunk, behind rear seatback. Controls: Super Handling All-Wheel Drive (SH-AWD) rear differential clutches. All part numbers are interchangeable, with 48310-RJC-A09 being the final superseded version.
We Have This Part in Stock
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- Acura RL: