C1241: Low or high power supply voltage to the skid control (ABS/VSC) ECU (Toyota)

ABS/VSC module supply voltage too low or too high

Severity: Inspect soon

Toyota's service manual says the skid control ECU stops ABS and VSC operation while this fault is present, and Toyota's owner's manual says an ABS or slip indicator light means the car should be inspected by a dealer immediately. Normal brakes should still work, but anti-skid help is gone.

It gets more serious if:

Stop: The red brake system warning light comes on, a brake warning message appears, or the brake pedal feels soft or different. Toyota says to stop in a safe place and contact a dealer, because continuing to drive may be dangerous.

Safety-critical system: explanation only, no DIY steps. Source: how we rate severity

C1241 in short

On Toyotas, C1241 means the ABS/VSC control unit saw its power supply voltage go too low or too high, so it turned anti-lock braking and stability control off. A weak battery or charging fault is a common trigger. Normal brakes should still work, but have it inspected promptly.

The skid control ECU runs the anti-lock brakes (ABS), traction control and stability control (VSC). It watches the battery voltage at its own power terminals. Toyota's repair manual says it stores C1241 when that voltage stays too low while driving or too high with the ignition on, and that the ECU stops ABS and VSC working until the fault clears.

The manual's checks start with the ABS fuse, then battery voltage (it expects about 10 to 14 V) and the charging system, then the power wiring to the ECU, and only then the ECU itself.

On 2006–2011 Highlanders, Highlander Hybrids and 2010–2014 Priuses, owners often report C1241 stored with brake accumulator or pump codes such as C1253, C1256 and C1391, together with brake warnings. In those cases dealers usually replaced the brake actuator or booster pump assembly. Those other codes should be diagnosed first.

Pick your make

C1241 is a manufacturer-specific code: its meaning depends on who built the car.

Other makes: meaning not verified. Check with a scan tool that reads manufacturer definitions.

C1241 on Toyota

Most likely causes

Cause 1: Weak 12 V battery or charging system fault
Supported by vehicle data
Why it ranks here
Toyota's repair manual lists the battery and charging system first and has the technician check battery voltage before anything else. Some owners were told by dealers to replace or charge the battery for this code.
What would change this
Rises if the battery is old, the car has been hard to start, or the code set after a jump start or flat battery. Falls if battery and charging voltage test normal.
Cause 2: Brake actuator or booster pump fault (Highlander, Highlander Hybrid, Prius)
Supported by vehicle data
Why it ranks here
On these models owners and dealers report C1241 together with accumulator and pump codes (C1253, C1256, C1391), and the brake actuator or booster pump assembly being replaced.
What would change this
Rises if C1253, C1256 or C1391 are stored too, or the brake pump runs often or noisily. Falls if C1241 is the only code.
How to test the brake system control module (abs module)
Cause 3: Blown ABS fuse or poor power feed to the ECU
Possible — needs testing
Why it ranks here
Toyota's repair manual names the ECU power source circuit as a trouble area and has the ABS fuse checked first.
What would change this
Rises if a fuse is blown or the connector is loose or corroded. Falls if the feed holds voltage with the code active.
Cause 4: Faulty skid control ECU
Possible — needs testing
Why it ranks here
Toyota lists the skid control ECU last, to replace only when battery, charging and wiring check good. One Sequoia owner reports a dealer replacing a shorted ECU.
What would change this
Rises only after the battery, charging system, fuse and wiring all test good.
How to test the brake system control module (abs module)

What to test first

Start at step 1. Each result tells you what it means and where to go next.

Step 1: Have all ABS/VSC codes read with a scan tool that can talk to the ABS module, and write down every code, not just this one.
Low riskTool: scan tool with ABS access
- IfC1253, C1256, C1391 or other brake pump or accumulator codes are stored too
  It meansThe brake actuator or pump is the more likely source; those codes come first.
  Go to step 3 Points to: Brake actuator or booster pump fault (Highlander, Highlander Hybrid, Prius)
- IfC1241 is the only brake code
  It meansStart with the battery and charging system.
  Go to step 2
Step 2: Have the 12 V battery and charging system tested. Many parts stores do this free. Toyota's manual expects about 10 to 14 V at the battery.
Low riskTool: battery and charging system tester
- IfThe battery fails the test or charging voltage is out of range
  It meansFix the battery or charging fault, then have the code cleared and rechecked.
  Points to: Weak 12 V battery or charging system fault
- IfBattery and charging test good
  It meansThe fault is more likely in the ECU power feed or the ECU.
  Go to step 3
Step 3: Have a technician check the ABS fuse, the power circuit and connector at the skid control ECU, and any brake pump or accumulator codes, using Toyota service information. Then clear the codes and recheck.
Best left to a shopTool: Toyota-capable scan tool and service information
Warning:This is brake system work. On hybrids the brake system holds high pressure. Do not open brake lines or the actuator yourself, and do not drive if the red brake light is on or the pedal feels wrong.
- IfA fuse or power circuit fault is found
  It meansRepairing the power feed is the fix.
  Points to: Blown ABS fuse or poor power feed to the ECU
- IfPump or accumulator faults are confirmed
  It meansThe brake actuator or booster pump assembly is suspect.
  Points to: Brake actuator or booster pump fault (Highlander, Highlander Hybrid, Prius)
- IfPower, wiring and battery are good and the code returns
  It meansThe skid control ECU is suspect.
  Points to: Faulty skid control ECU

Symptoms

ABS warning light on
VSC or slip indicator light on, sometimes with the check engine light
Brake warning light or Brake Malfunction message Gets more serious: stop and have it checked.
Brake pump running often or making a buzzing noise (hybrids, Highlander)

How to fix

This is a safety-critical system, so we explain the code but don't give repair steps. Have it inspected by a qualified technician.

Parts and cost context

Brake actuator / booster pump assembly:Owners report dealers replacing this on Highlander, Highlander Hybrid and Prius when C1241 comes with pump or accumulator codes. Have the battery and charging system checked first. Labour varies; get a quote.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Toyota

2002–2003 · Sequoia
Supported by vehicle data
Owners report C1241 with VSC, TRAC and ABS lights, sometimes stored with C1203 or C1223; one dealer replaced a shorted skid control ECU. We found no Toyota bulletin naming C1241.
2006–2011 · Highlander
Supported by vehicle data
Highlander and Highlander Hybrid owners report C1241 with C1253, C1256 or C1391, brake and VSC warnings, and dealers replacing the brake actuator or pump assembly.
2010–2014 · Prius
Supported by vehicle data
Owners report C1241 with brake booster pump or accumulator codes and brake warnings; dealers quoted replacing the brake booster and pump assembly.

All ABS, traction and stability control codes

C1241 questions

Can a bad battery cause C1241?

Yes. Toyota's repair manual lists the battery and charging system as the first things to check, because the code means the ABS/VSC unit saw its supply voltage go out of range.

Is it safe to drive with C1241?

Normal brakes should still work, but ABS and stability control are off, so have it inspected promptly. If the red brake light comes on or the pedal feels wrong, stop in a safe place and get help.

Sources and review

Camry Owner's Manual (OM06291U) — Toyota
2005 Toyota Sequoia repair manual: DTC C1241/41 power source circuit — Toyota Motor Corporation (third-party mirror)
Owner complaints mentioning C1241 on Toyota vehicles — NHTSA Office of Defects Investigation
NHTSA complaint 10763495: 2006 Toyota Highlander Hybrid, dealer codes C1241, C1256, C1391 — NHTSA Office of Defects Investigation
NHTSA complaint 10315765: 2002 Toyota Sequoia, dealer finds C1241 — NHTSA Office of Defects Investigation
2005 Toyota Sequoia repair manual: ABS/VSC diagnostic trouble code chart — Toyota Motor Corporation (third-party mirror)

Last reviewed: October 15, 2026
Written by: Saurabh K.
Editorial review: Pending
Technician review: Technician review pending

This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error

Severity: Inspect soon

Pick your make

Most likely causes

Cause 1: Weak 12 V battery or charging system fault

Cause 2: Brake actuator or booster pump fault (Highlander, Highlander Hybrid, Prius)

Cause 3: Blown ABS fuse or poor power feed to the ECU

Cause 4: Faulty skid control ECU

What to test first

Step 1: Have all ABS/VSC codes read with a scan tool that can talk to the ABS module, and write down every code, not just this one.

Step 2: Have the 12 V battery and charging system tested. Many parts stores do this free. Toyota's manual expects about 10 to 14 V at the battery.

Step 3: Have a technician check the ABS fuse, the power circuit and connector at the skid control ECU, and any brake pump or accumulator codes, using Toyota service information. Then clear the codes and recheck.