How to Clear Service 4WD Light: 10 Steps

If you own a 4WD vehicle or are into off-roading, you may have seen a flashing Service 4WD light at some point. The experience can be unnerving for less experienced drivers, and rightfully so — as this warning light can lead to serious problems and even damage to the vehicle if not addressed. In this guide, let’s look at what this warning light means and how to reset it.

Clearing the Service 4WD light involves thoroughly inspecting related components and testing for voltage and resistance in its power source and control modules. The process is relatively straightforward for the mechanically inclined but may sometimes require a professional mechanic.

The owner’s manual is your best bet for OEM-specific instructions on getting this issue resolved. But if you need a quick reference, here are the 10 steps on how to clear your Service 4WD light:

1. Check the Owner’s Manual.
2. Inspect the 4WD System.
3. Disconnect the Battery and TCCM.
4. Remove the Knee Bolster and Dash Bezel.
5. Check the Wiring and Switch Assembly.
6. Check the Transfer Case and TCCM.
7. Check the 4WD Control Module.
8. Reinstall Interior Panels.
9. Perform a System Reset.
10. Take Your 4×4 to a Professional.

The 4WD system is fundamental to a vehicle’s proper operation and safety on the road. But when compromised, it dampens the ability of your wheeler to navigate slick surfaces and challenging terrain.

Because of the seriousness of these repercussions, neglecting the Service 4WD Light and any issues with the system is ill-advised — as they can result in expensive repairs and jeopardize safety on the road.

What the Service 4WD Light Means

An illuminated or blinking Service 4WD Light indicates a problem with the 4WD system in a vehicle picked up by the computer system. The onboard computer system may notify the driver of an incomplete shift in the gear, impending engine damage, or other issues that require immediate service.

Several factors can trigger the Service 4WD light, including a malfunctioning or overheated transfer case, damaged or corroded wiring, and other issues with the 4WD system. Other things that can set it off are:

• Low or contaminated fluid levels.
• Worn-out or damaged components.
• Damaged differential axles.
• Electrical or sensor problems.

Occasionally, a flashing Service 4WD light isn’t a cause for concern, as it only means your 4WD system is working as it should. This applies to 4x4s with On-Demand 4WD layouts, such as Volkswagen, Jeep, and Honda.

How to Clear Service 4WD Light

1. Check the Owner’s Manual.

The owner’s manual provides crucial information on how to take care of your four-wheeler and what to do if something goes wrong. It also contains information on the Service 4WD Light and how to troubleshoot the problem.

Read the section on warning light indicators carefully and follow the instructions provided if you suspect your Service 4WD light is signifying something amiss with your 4WD system.

2. Inspect the 4WD System.

Before attempting to clear the Service 4WD light, it’s important to inspect the 4WD system and ensure it is working correctly.

To do this, engage the 4WD and see if the system responds accordingly to driver inputs. If not, there may be a problem with the wiring, switches, transfer case, or 4WD system and its components.

3. Disconnect the Battery and TCCM.

Disconnecting the battery is one of the easier methods of clearing the Service 4WD Light on your dash. Doing so resets the onboard computer system in your 4×4 and clears the warning light (albeit not in all cases).

Another quick way to reset your 4WD system is to unplug the TCCM (Transfer Case Control Module). The order of these quick fixes are interchangeable — it is advisable to disconnect the battery first before tinkering with the control module.

To disconnect the battery, first, turn off the engine. Next, use a wrench to remove the negative cable from the battery terminal. Wait for 15 minutes to an hour before reconnecting the cable. If the culprit behind your flashing Service 4WD light is minor, this trick should eliminate the root problem.

4. Remove the Knee Bolster and Dash Bezel.

If step #3 (a.k.a. soft reset) does not work, it is time to check the knee bolster and dash bezel.

The former is an interior trim component typically located under the steering column, whereas the latter is the piece surrounding the gauges and instrument cluster on your 4×4’s dashboard. Removing both will give you access to electrical components or switches warranting service or replacement.

Refer to your owner’s manual for instructions on removing these pieces properly.

5. Check the Wiring and Switch Assembly.

Once you remove the knee bolster and dash panel, pull on the switch assembly and check the relevant wiring. Doing so lets you know if your 4WD service light issue is due to a switch/wire fault or something more intricate.

Even if you are extremely careful with your vehicle and how you drive, the wiring for your 4WD system can become damaged or corroded due to age, poor installation, or other electrical faults in your wheeler.

6. Check the Transfer Case and TCCM.

If the battery and electrical connectors check out, the TCCM (Transfer Case Control Module) is often to blame. After all, it is responsible for transfer case operability, which facilitates power distribution toward the front and rear axles in a 4×4. Moreover, this module monitors inputs from various sensors and switches apart from the transfer case.

Visually inspect the transfer case. Check fluids, look for leaks, and scrutinize the linkage between the transfer case and the 4WD control lever while at it.

Locate the fuse box and check if any fuses related to the 4WD system and TCCM are blown and require replacement. If yes, get replacement fuses of the same amperage.

Examine the wiring and connectors leading to the TCCM for any damage, corrosion, or loose connections. Again, repair or replace compromised wiring or connectors as needed.

Fault Codes:

Using a diagnostic scanner like the Autel MaxiSys MS906 Pro-TS Diagnostic Scan Tool (view on Amazon), read any fault codes stored in the TCCM. Some examples of fault codes signifying issues with the TCCM or the 4WD system in Ford vehicles include P1867, P1875, P1860, and P1887 (see descriptions for each below):

• P1867: Transmission Transfer Case Contact Plate General Circuit Failure
• P1875: Transmission Automatic Hall Effect Sensor Power Circuit Short To Battery / 4WD Low Switch Circuit Electrical
• P1860: TCC PWM Solenoid Circuit Electrical / Transmission Transfer Case Contact Plate ‘D’ Short Circuit To Battery
• P1887: 4-Wheel Drive Control Solenoid Circuit Failure

Resolve the diagnostic trouble codes in the order they appeared on your scanner. After which, test the control module by commanding it to engage and disengage the transfer case while monitoring the system response.

You may utilize the same diagnostic scanner that retrieved the fault codes or a TCCM-specific tool. Monitor how the transfer case toggles to ensure it is working correctly.

If all else fails, replace the TCCM. Do this only if you are mechanically savvy. Otherwise, outsource this step to a qualified mechanic, which may involve programming the new module.

7. Check the 4WD Control Module.

If the battery, wiring, and transfer case are all in good condition, the next step is to check the 4WD Control Module. I know what you are thinking — “I have just finished this step, so why do it again? Besides, the TCCM is the 4WD Control Module, right?” Well, not exactly. Yes, all TCCMs are 4WD control modules. But not all 4WD control modules are TCCMs.

Depending on your vehicle type, you may or may not need to do this step. In general, most 4x4s with an electronically-controlled 4WD system would have a dedicated TCCM controlling how the transfer case is toggled.

In this setup, however, the TCCM may be integrated with the PCM or BCM, depending on the vehicle’s design.

Steps:

1. Perform a visual inspection of the 4WD system and all related components for obvious signs of damage, wear, or corrosion. Keep an eye out for any loose connections or wiring issues.
2. Like the TCCM, scan your 4×4 for error codes using a diagnostic scanner.
3. Check the control module power supply by testing the voltage and resistance of the wiring and connections. For this bit, use a multimeter — preferably a digital one like the Fluke 87V MAX/E2 KIT True-RMS Digital Multimeter Combo Kit (view on Amazon) — and refer to your owner’s manual for OEM-recommended values.
4. Next, test the 4WD control module outputs and inputs using a diagnostic scan tool, multimeter, or oscilloscope. Approach this step the same way you would when testing the power supply — by including voltage, resistance, and a visual inspection of wiring and components — on top of checking the modlule’s ability to send and receive signals uninterruptedly from other 4WD system components.
5. Lastly, perform a system functional test by engaging and disengaging the 4WD system while monitoring the control module outputs and inputs.

Popular name brands commonly using separate TCCM and 4WD control modules are as follows. (For other vehicle makes, check the owner’s manual if you need to work on two control modules.):

• Ford
• Chevrolet/GMC
• Dodge/Ram
• Jeep
• Toyota
• Nissan

8. Reinstall Interior Panels.

Reinstall the knee bolster and dash panel, properly securing and tightening all vacuum lines, fasteners, and electrical connectors. Depending on your vehicle, you may need to put these panels back in their place before testing the transfer case and 4WD control modules.

9. Perform a System Reset.

At this point, your Service 4WD Light should have stopped blinking. If it hasn’t, it may be necessary to perform a system reset. This can be done using an OBD-II or DRB-III diagnostic scan tool.

Depending on what has triggered your service 4WD light and how bad the issue is, you may need to do a simple reset of the 4WD system and affected control modules or a complete onboard computer reset.

10. Take Your 4×4 to a Professional.

Even for mechanically-savvy vehicle owners, going through steps #1—9 can be a grueling, time-consuming ordeal. But if that isn’t bad enough, the turnout could be unsuccessful sometimes. If that happens, hold your head up high — it’s okay to call on the experts for help.

Can I Still Drive with Service 4WD Light On?

Because driving with the Service 4WD Light on can lead to serious problems, it is NOT RECOMMENDED. As established early in this guide, this warning light indicates an issue with the 4WD system that can adversely affect a vehicle’s handling, stability, and safety.

If you keep driving with the warning light on, you only risk causing further damage to your vehicle’s drivetrain (not to mention putting yourself and your passengers in danger).

Conclusion – How to Clear Service 4WD Light

To summarize, here are the 10 steps on how to clear the Service 4WD Light on your vehicle:

1. Check the Owner’s Manual.
2. Inspect the 4WD System.
3. Disconnect the Battery and TCCM.
4. Remove the Knee Bolster and Dash Bezel.
5. Check the Wiring and Switch Assembly.
6. Check the Transfer Case and TCCM.
7. Check the 4WD Control Module.
8. Reinstall Interior Panels.
9. Perform a System Reset.
10. Take Your 4×4 to a Professional.

Whether driving off-road or on slick highways, the 4WD system is integral to your vehicle’s safety and performance. Ignoring the Service 4WD Light is not an option — and thankfully, you do not have to.

By following the process outlined in this article (and instructions in your manual), you can easily clear the warning light and get your vehicle back to performing at its best.