DISPLAY_LABEL: Brake System Signal Plausibility Fault
SAE J2012-classified chassis code C0764 indicates a chassis-level fault related to a brake-system signal that the vehicle control logic considers implausible or inconsistent. The exact component or sensor tied to C0764 varies by make, model, and year; manufacturers map the same chassis code to different inputs in their control modules. You must confirm the true source with simple electrical and network checks rather than assuming a specific failed part. Test power, ground, connector integrity, wiring continuity, and the communication bus before any replacement.
What Does C0764 Mean?
C0764 is a chassis-category Diagnostic Trouble Code (DTC) that refers to an unexpected or implausible brake-related signal reported to a vehicle control module. Under SAE J2012 formatting the code structure and basic wording are standardized; the SAE J2012-DA digital annex publishes standardized DTC descriptions used for cross-reference. Many chassis and body codes do not have a single universal component-level definition, so the OEM’s service documentation or module data is needed to map the code to a specific input.
The code shown here is presented without a hyphen FTB (Failure Type Byte) suffix. An FTB, when present (for example -1A or -63), acts as a subtype that narrows the failure mode or location information reported by the module; absence of an FTB means you have the base code only and must rely on tests and freeze-frame data to determine the precise failure behavior.
Quick Reference
- System: Chassis — brake signal plausibility or circuit inconsistency
- Primary checks: power, ground, connector integrity, wiring continuity
- Network checks: CAN/LIN message presence and plausibility
- Data sources: freeze-frame, live data, and Mode 06 or manufacturer diagnostics
- Diagnosis approach: test-driven — verify wiring and signals before module replacement
Real-World Example / Field Notes
Technicians commonly find C0764 after an intermittent ABS or brake warning lamp and when live data shows a wheel-speed or brake-pressure value that jumps, drops to zero, or disagrees with other sensors. In one shop case the freeze-frame showed a sudden zero signal from a speed input while neighboring channels remained steady; inspection revealed a corroded pin at a harness splice. In another case the control module logged the code during a battery replacement when a poor engine-ground strap produced noisy measurements.
Practical checks that often locate the fault quickly include backprobing the sensor connector to verify reference power and ground, wiggle-testing the harness under load to reproduce an intermittent fault, and comparing the suspect channel to other redundant sensors for plausibility. If the module reports inconsistent data but wiring and connectors test good, confirm the presence and integrity of CAN or LIN messages with a scope or a good-quality scan tool before considering the module’s internal processing or input-stage issue.
When documenting field findings, capture freeze-frame values and live-data logs while exercising the system (apply braking, rotate the wheel, or induce the reported condition) so you can prove whether the sensor signal itself is implausible or whether a wiring, power, ground, or communication fault is corrupting the reading.
DISPLAY_LABEL: Chassis Circuit Fault – Brake Control Signal
The SAE J2012-DA format defines DTC structure and standard wording; many chassis codes like C0764 point to a circuit-level problem in a brake-related control or sensor circuit rather than a single universal part. Exact component interpretation can vary by make, model, and year. Confirming the cause requires test-driven electrical and network checks: verify power and ground, inspect connectors and wiring, and confirm signal plausibility with a scan tool and diagnostic meter or oscilloscope before replacing components.
Symptoms of C0764
- Warning lamp: A brake or traction control-related warning lamp or indicator may illuminate on the dash.
- ABS/ESC intervention: Unexpected ABS, ESC, or traction-control activation or reduced performance messages during normal driving.
- Pulsing brake feel: Unusual brake pedal feedback such as pulsing or a change in pedal firmness under braking.
- Erratic speed readings: Inconsistent wheel speed or vehicle speed readouts on a scan tool or gauge when compared across sensors.
- Communication errors: Loss of messages or error frames on the vehicle network when interrogating control modules.
Common Causes of C0764
Most Common Causes
- Intermittent or corroded wiring/connectors in the brake control sensor or actuator harness — commonly associated with moisture intrusion or vibration.
- Loss of power or ground to the brake control circuit due to a blown fuse, poor chassis ground, or connector contact resistance.
- Signal plausibility failure where the control module sees values outside expected ranges — often caused by sensor mismatch, wiring short to voltage/ground, or intermittent connections.
- Network message faults on the Controller Area Network (CAN) or Local Interconnect Network (LIN) preventing reliable data exchange between brake module and other controllers.
Less Common Causes
- Internal input-stage issue in a control module after all external wiring, power, ground, and bus checks pass.
- Mechanical sensor contamination or magnet/electromagnetic interference affecting signal integrity.
- Aftermarket modules or loose module mounting causing poor ground or electrical noise.
Diagnosis: Step-by-Step Guide
Tools: professional scan tool with live data and component tests, digital multimeter (DMM), oscilloscope or lab scope, backprobe pins, wiring diagrams, insulated jumper set, contact cleaner, and a basic hand tool set.
- Read and record the freeze frame and DTC details with a full-feature scan tool; note if the code includes a Failure Type Byte (FTB) suffix. If no FTB is present, treat the code as a base circuit fault; an FTB would narrow the failure subtype.
- Check for stored network errors and module availability on the CAN/LIN bus. Confirm the brake-related module appears and responds to the scan tool; lack of presence suggests bus or power/ground problems.
- Inspect connectors and wiring at the suspected harness runs: look for corrosion, bent pins, damaged insulation, or poor connector seating. Wiggle harnesses while watching live data for intermittent change.
- Verify power and ground at the module and at the sensor/actuator harness with a DMM. Measure battery voltage at the module power pin under key-on and engine-off conditions and check resistance to chassis ground for good connections.
- Measure sensor or actuator signals with an oscilloscope or high-resolution DMM while operating the system or rotating the wheel (if safe). Compare waveform shape and amplitude to known-good patterns or service data; implausible shapes indicate wiring shorts/noise or a bad sensor.
- Perform continuity and short-to-power/ground tests on suspect wires with key off. Repair any opens or shorts found, then retest for proper signal and absence of DTCs before proceeding.
- If wiring, power, and ground test good, monitor Mode $06 or live data for plausibility limits and perform factory bidirectional tests if the scan tool supports them to command actuators and observe responses.
- If all external checks pass and the module shows corrupted inputs or fails to process valid signals, consider module-level diagnostics—suspect an internal input-stage issue only after confirming all external wiring and network integrity.
- Clear codes and perform a road test or system exercise. Re-scan to confirm the fault does not return. If intermittent, reproduce the conditions that set the code and focus on harness movement and environmental factors.
Professional tip: Always verify the simplest electrical path first—good power and ground and a solid CAN/LIN presence eliminate many false leads. Use backprobes and an oscilloscope to prove real-time signal quality before condemning sensors or modules.
DISPLAY_LABEL: Chassis Brake Sensor Signal Plausibility
Base repairs must be driven by measured signal values, continuity checks, and connector inspections. Use a DMM, oscilloscope, scan tool with live data and CAN checks to confirm the fault before replacing hardware. Many C-codes vary by make and model; treat C0764 as a chassis-level brake sensor/circuit plausibility issue and verify wiring, power, and communication first.
Possible Fixes & Repair Costs
Low-cost fixes: wiring repair, connector cleaning, or corroded terminal replacement when a continuity test or wiggle test shows intermittent open or high resistance. Low: $40–$150. Typical fixes: replace a damaged sensor or a single harness section when bench or in-situ sensor output is out of range and connector/power/ground test results are good. Typical: $150–$450. High-cost fixes: multi-module troubleshooting, ECU harness replacement, or module replacement if all external wiring, power, ground, and bus messaging check good and scoped signals still fail. High: $450–$1,200.
Each recommended fix must be justified: choose wiring repair when continuity and insulation resistance tests fail; choose sensor replacement when bench/known-good sensor tests show correct output but vehicle sensor does not; choose module-level service only after power, ground, input signals, and CAN/LIN reporting are confirmed good. Labor rates and parts availability, access difficulty, and needed calibration/programming (if required by OEM) affect the final bill.
Can I Still Drive With C0764?
You can often drive short distances with C0764 present, but it depends on vehicle failsafe behavior. If the code reflects a sensor plausibility issue in an ABS/ESC (Electronic Stability Control)/TCS (Traction Control System) input, those systems may be limited or disabled, increasing braking and stability risk in low-adhesion conditions. Confirm whether the ABS/ESC warning lamp is lit and test drive cautiously on low-risk roads only after verifying no additional warnings appear.
What Happens If You Ignore C0764?
Ignoring C0764 can leave braking and stability assistance degraded or disabled. That raises the chance of longer stopping distances or loss of traction control under emergency or slippery conditions. Intermittent faults can also lead to unpredictable system behavior and additional electrical damage if left unresolved.
Related Codes
- C0767 – Brake Control Signal Plausibility (Chassis)
- C0766 – Tire Pressure Monitor System – High Tire Pressure
- C0765 – Wheel Speed Sensor Signal Plausibility - Chassis
- C0763 – Steering Sensor Signal Plausibility
- C0762 – Brake Pressure Signal Plausibility
- C0761 – Brake Pressure Signal Plausibility
- C0759 – Steering Assist Communication Fault
- C0758 – Tire Pressure Monitor Sensor Circuit Range/Performance
- C0757 – Steering Angle Signal Circuit Fault
- C0756 – Steering Angle Signal Plausibility (Chassis)
Key Takeaways
- Treat C0764 as a chassis-level brake/sensor plausibility fault under SAE J2012-DA.
- Do test-driven diagnosis: power, ground, continuity, signal amplitude/frequency, and bus checks.
- Repair decisions must be backed by specific measurement failures or connector/harness damage.
- Module replacement is a last resort after all external inputs and communications test good.
Vehicles Commonly Affected by C0764
C0764 is commonly seen on vehicles with advanced ABS/ESC architectures and multi-sensor wheel-speed networks; examples often reported include certain European and Japanese cars and modern SUVs. Systems with distributed wheel-speed sensors, multiple control modules, or complex CAN/LIN routing are more likely to surface plausibility faults due to wiring damage, connector corrosion, or sensor signal degradation. Interpretation and repair steps can vary by make/model/year.
FAQ
Can a bad wheel speed sensor cause C0764?
Yes, a wheel speed sensor that produces implausible amplitude, frequency, or intermittent signals can trigger C0764, but you must confirm with tests. Use a digital multimeter for resistance, an oscilloscope for waveform and amplitude under wheel rotation, and a scan tool to compare live data across sensors. Replace the sensor only after bench or in-vehicle signal tests show it is out of specified behavior while wiring and connectors test good.
Is module replacement usually required for C0764?
Module replacement is not usually the first step. Only consider possible internal processing or input-stage issue after you verify power, ground, wiring continuity, connector integrity, and correct sensor signals and CAN messages. If all external inputs and network communication test good and the module shows no internal diagnostics for input failures, then further module-level diagnostics or replacement may be warranted as a last resort.
Can poor ground or power cause this code?
Absolutely. Erratic or low supply voltage and poor ground return can make a sensor appear implausible. Start by measuring key circuit supply voltages at the sensor connector with the ignition on and engine off, check ground resistance to chassis, and perform wiggle tests while monitoring live data. Fix a bad power or ground if voltage drops, high resistance, or intermittent loss correlate with the fault.
How do I confirm it’s a wiring/connectivity issue?
Confirm wiring issues with continuity and resistance checks between the sensor connector and the control module, inspect for corrosion or pin damage, and perform wiggle tests while monitoring live data for changes. Use an oscilloscope to see signal dropouts or noise. If a known-good sensor produces correct signals when connected to the suspect harness, wiring or connector repair is justified.
Will a scan tool confirm C0764 is intermittent?
A scan tool with freeze frame and live-data logging can show whether the fault is intermittent. Use long-duration datalogging while driving or simulating wheel rotation to capture signal outages or plausibility failures. If the code appears without corresponding live-data anomalies, expand testing to power, ground, and bus integrity to find intermittent harness or connector issues before replacing components.