4Runner ABS codes — How to fix

LED and HID Retrofit Headlights cause  Toyota 4Runner ABS codes C0226, C0236, C0246 and Co256

Toyota has issued a service bulletin T-TT-0597-20 to address Toyota 4Runner ABS codes C0226, C0236, C0246 and Co256 on 2012-20 Toyota 4Runner vehicles. Toyota refers to their ABS system as Skid Control. Toyota is finding that owners who retrofit their vehicles with aftermarket LED or HID bulbs may be causing the ABS-related trouble codes to set.

Cause of Toyota 4Runner ABS codes C0226, C0236, C0246 and Co256

Radiofrequency interference (RFI) caused by aftermarket LED bulbs and HID ballasts may cause electrical noise on the ground side of the skid control circuit. If you experience any of the trouble codes shown above, clear the codes and drive the vehicle with the headlights off. If the codes do not reappear, change the headlights back to the factory style.

There is not other fix for this problem. LED and HID retrofit kits simply give off way too much RFI and are not compatible with your 4Runner.

Rettrofit LED bulbs are not street legal and cause other problems as well

Using LED bulbs in fixtures not designed for them can lead to a host of problems that outweigh the potential benefits. While LEDs are highly energy efficient and long lasting, retrofitting LEDs into traditional housings can result in light quality issues, overheating, early failures, and safety concerns.

One major issue with using LED bulbs in old fixtures is inconsistent light output and distribution. Traditional bulbs emit light in all directions which reflects off the housing to spread light effectively. LEDs emit directional light which often does not properly illuminate the intended area when used in outdated housings. This can leave dark spots or an uneven lighting pattern. The housing was simply not engineered to work with the focused beam of an LED.

Heat dissipation is another problem in retrofit situations. LEDs require ambient cooling which is facilitated by specially designed housings. Older fixtures do not allow proper dissipation of heat generated by LEDs which can cause them to overheat, stressing the components and shortening the bulb’s lifespan significantly. This eliminates the longevity benefit of LEDs.

Safety is also a concern when using LED retrofit bulbs. The mismatched use can lead to electrical issues like overloading circuits, and the RFI interference described above.

While LEDs can provide amazing efficiency and lighting quality, you can’t simply swap them into a headlight designed for halogen bulbs. In fact, it is optically impossible for a retrofit LED bulb to produce the proper beam pattern when used in a halogen headlight.

©, 2021 Rick Muscoplat