C115A

Code

Generic C — Chassis

ABS Control Module Internal Fault

Brand: Generic

Type: C — Chassis

Views: UK: 3 EN: 3 RU: 6

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Page language: EN

Causes

Internal ABS control module hardware failure (power stage, processor, memory).
Corrupted module software/firmware.
Intermittent or low power supply to the ABS module (battery, ground, fusible link).
CAN or vehicle network communication faults interfering with module operation.
Water intrusion, corrosion, or physical damage to the ABS module or connector.
Shorts or opens on power/ground/sensor wiring causing module stress.

Symptoms

ABS / traction control warning lamp illuminated.
Possible stability control/ESC warning.
ABS inoperative — no anti-lock function during braking.
Intermittent or permanent loss of wheel speed data on diagnostic tool.
Vehicle limp behavior or reduced braking performance messages.
Stored freeze frame or network communication errors alongside C115A.

What to check

Read all stored codes from all control modules (ABS, engine, transmission, BCM, instrument cluster).
Check battery voltage at rest and during cranking (should be ~12.4–12.8 V resting, >13.5 V with engine running).
Inspect ABS module connector for corrosion, bent pins, water intrusion, or damaged insulation.
Check fuses and fusible links feeding the ABS module and related sensors. Replace or test as needed.
Scan CAN bus for lost communication or U-codes (e.g., U0121). Verify CAN high/low voltages at the ABS module connector.
Check wheel speed sensor signals and wiring for shorts/opens and compare all four corners.

Signal parameters

Module supply voltage: nominal 11–15 V; significant drops or spikes indicate power issues.
Ignition-switched 12 V supply present when key ON; measure at module power pin.
Ground continuity: near 0 ohms from module ground pin to chassis ground.
CAN bus differential voltage: approx. 2.5 V common mode, CAN_H ≈ 2.5–3.5 V, CAN_L ≈ 1.5–1.0 V when idle (varies by vehicle).
Wheel speed sensor signals: passive sensors produce AC pulses with amplitude rising with speed; active/Hall sensors produce 0–5 V square/pulse signals. Compare waveform symmetry and amplitude across sensors.
Module current draw: abnormal high current may indicate internal short (requires manufacturer spec).

Diagnostic algorithm

Record all codes and freeze-frame data from the ABS and other modules. Note if C115A is accompanied by communication codes.
Verify battery condition and charging system. Recharge or replace battery if low; ensure charging >13.5 V with engine running.
Visually inspect ABS module and harness: connector seals, pins, signs of moisture, corrosion, or physical damage. Repair or clean as required.
Check fuses and input power/ground to the ABS module with ignition ON. Repair wiring or replace blown fuses.
Use a lab scope or scan tool to monitor CAN bus activity at the module while operating ignition; look for dropped messages or abnormal levels. Repair wiring/terminations if needed.
Measure wheel speed sensor signals/wiring at the sensor and at the ABS module while rotating the wheel (or road test). Verify all sensors produce expected pulses and have correct resistance per vehicle spec.
If power, ground, network, and sensors check good, attempt module reset/clear codes and re-run tests. If code returns immediately, likely internal module failure.
Consult manufacturer service information for module reprogramming or software updates; apply updates if available.
If confirmed internal fault and no wiring/power/network cause is found, replace ABS control module and program/codeto vehicle per manufacturer procedure.
After repair, clear codes and perform ABS/ESC system self-test and road test to confirm proper operation.

Likely causes

Failed internal components in ABS module (voltage regulator, processor, EEPROM).
Poor battery/charging system voltage or poor ground to ABS module.
Damaged ABS module connector pins or corrosion.
Loss of CAN bus termination or wiring short affecting module comms.
Prior repair or improper programming that corrupted module software.

Fault status

⚠️ Status

ABS Control Module — internal electronic or software fault detected. ABS/ESC functionality may be reduced or disabled. Investigation of power, ground, network, and module integrity required.

🔴 Repair difficulty: Hard

⏱️ Diagnostic time: 1.5-4 hours

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