C1A00: How to Diagnose & Fix — Stability Control System Fault
4 vehicles · 4 makes · $300-$3,500 repair
How to diagnose and fix C1A00: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Land Rover Discovery · 2005–2016
The Terrain Response system on the LR3/LR4 develops faults where mode selection fails or the system defaults to General mode only. The rotary selector switch wears out internally, and the shift motor on the transfer case can fail. Corroded connectors at the transfer case are a common root cause. The vehicle remains drivable in General mode but loses off-road capability.
Common Symptoms
- Terrain Response fault on dashboard
- Unable to change terrain modes
- Stuck in General/Normal mode
- HDC (Hill Descent Control) fault
- Low range not engaging
How to Fix
Clean and inspect the Terrain Response selector switch and connectors. Replace the shift motor on the transfer case if faulty. Check the transfer case wiring harness for corrosion — a common failure point is the connector near the exhaust. Update the transfer case ECU software at a dealer.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- IGH500040 transfer-case shift motor assemblyOEMIGH500040
Replace a command- and circuit-test-confirmed failed transfer-case shift actuator Fitment/availability: Discovery 3 and Discovery 4 with the applicable transfer case. Confirm VIN, two-speed transfer-case equipment, motor failure and curr…
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Owner tips & cautions
- TipBefore replacing expensive parts, clean all the connectors at the transfer case with electrical contact cleaner. Corrosion here causes 70% of Terrain Response faults.
MINI Cooper · 2014–2025
F56 generation Coopers experience electric power steering rack failures. The EPS motor or control module within the rack fails, causing sudden loss of power assist or intermittent heavy steering. This is a safety concern as it can happen while driving.
Common Symptoms
- Power steering warning light
- Sudden heavy steering
- Intermittent power steering loss
- Steering wheel vibration
- Clunking noise when turning
How to Fix
Replace electric power steering rack assembly. Unfortunately the EPS motor is integrated into the rack and cannot be serviced separately. Some rebuilt units are available at lower cost.
Ford Focus · 2012–2016
The 2012 Mk3 Focus was the first Focus with a fully electric rack-mounted power steering assist (EPAS). The torque/position sensor and motor assembly inside the rack, and the power steering control module (PSCM) integrated with it, fail intermittently - often heat-soaked on long drives or hot days. The dash shows "Power Steering Assist Fault - Service Now", the wheel goes heavy with no warning, and steering no longer self-centers. Failures are frequently intermittent at first (assist returns after a key cycle) and then become permanent. Because the assist motor is integral to the rack, Ford's repair is a complete steering gear replacement. Unlike the Fusion/Taurus/Flex family, which got NHTSA recall 15V340 for the same motor-sensor defect, the Focus was never recalled despite hundreds of NHTSA complaints, and was instead the subject of a class-action suit covering 2012-2014 Focus and Focus Electric.
Common Symptoms
- Power Steering Assist Fault - Service Now message
- Steering suddenly becomes very heavy while driving
- Assist comes back after restarting the car
- Steering does not return to center after a turn
- Fault appears more often on hot days or after long drives
How to Fix
Scan the PSCM for stored codes first (low battery voltage and corroded connectors at the rack can mimic the fault). If EPAS-internal codes are present, Ford's only repair is replacement of the complete electric steering gear assembly and PSCM software programming; some cars are fixed by a PSCM reflash alone when no hard codes are stored. Verify battery and alternator output before condemning the rack, since low system voltage will drop assist and set the same message.
Sources for this issue (5)
- Power steering assist fault | Focus Fanatics Forumforum
- Sudden and complete steering failure | Focus Fanatics Forumforum
- NHTSA Recall 15V340 - Ford, Failure of Electric Power Steering Assist (same motor sensor defect, Focus excluded)article
- Ford Steering Problems Come into Focus - Safety Research & Strategiesarticle
- 2012 Ford Focus Power Steering Failure: 122 Complaints - CarComplaintsarticle
Mitsubishi Eclipse Cross · 2018–2021
Find C1A00 by make
Browse every documented model and issue for your make.
C1A00 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does C1A00 mean?
C1A00 stands for "Stability Control System Fault." This is a chassis/stability-control code that signals a general fault within the electronic stability control system — the network of sensors and the controller that keep the vehicle from skidding or losing traction during hard cornering or slippery conditions. C1A00 typically means the stability control module detected an internal fault or a problem somewhere in the system it can't fully resolve, so it may disable stability and traction control and turn on the related warning lights. Importantly, C1A00 is a manufacturer-specific code and its precise meaning varies by brand, and the full code often includes additional sub-numbers needed to pinpoint the exact fault. Because it's broad, an accurate diagnosis usually requires a capable scan tool to read the extended code and any companion codes.
What are the most common causes of C1A00?
The most common causes of C1A00 are: Internal stability control module fault, Companion sensor faults (wheel speed, steering angle, yaw/lateral) triggering the system, Wiring, connector or ground problems in the stability control circuit, Low system or battery voltage / charging issue, Module software, calibration or configuration fault, Damaged or unplugged sensor harness after service, Faulty ABS/stability hydraulic control unit (less common). The specific cause varies by vehicle.
How much does it cost to fix C1A00?
Repair costs for C1A00 range from $300 to $3,500, depending on the vehicle and root cause.
Which vehicles are affected by C1A00?
Au7o has documented C1A00 across 4 vehicle models from 4 manufacturers: Ford, Land Rover, MINI, Mitsubishi.
Join 600+ people using Au7o to better understand their vehicles.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.