🚨 Diagnostic Profile
- Vehicle/Equipment Make: GENERIC
- Technical Description: Brake Booster Temperature Sensor C Circuit Intermittent/Erratic
Code C05B7 is a chassis-side diagnostic trouble code monitored by the Electronic Brake Control Module (EBCM), and in some platforms shared with the Power Steering Control Module. This code specifically targets ‘Temperature Sensor C’ within the brake booster assist circuit — a component responsible for relaying thermal data from the electro-hydraulic or vacuum-assist brake booster pump to the EBCM. When this code sets as ‘Intermittent/Erratic,’ it means the module is seeing voltage spikes, drop-outs, or out-of-range values from this sensor circuit that do not align with expected operating parameters. This is often caused by a chafed harness connector near the booster pump mounting bracket, corrosion inside the sensor pigtail connector, or a failing internal thermistor within the booster pump housing itself. Because the EBCM uses this temperature data to modulate brake assist pump duty cycles (preventing pump motor overheating during repeated hard stops or extended traction control events), an intermittent signal can cause the module to default to a conservative, reduced-assist safety strategy, resulting in a firmer brake pedal feel and an illuminated ABS or Brake warning indicator on the dash cluster.
🚨 Repair Difficulty Tier
- Difficulty Rating: Intermediate
This repair requires a bi-directional scan tool capable of reading live EBCM data streams (not just a generic code reader) along with a digital multimeter to verify resistance and voltage drop across the sensor circuit. While the diagnostic portion demands some technical know-how, the physical repair — typically a connector or sensor harness replacement — is manageable for an experienced DIYer with proper electrical safety precautions around the brake assist system.
🛠️ Resolution Steps
- Step 1: Preliminary Inspection
Visually inspect the wiring harness and connector leading to the brake booster pump assembly, checking specifically for the Temperature Sensor C pigtail. Look for melted insulation (a common sign of thermal stress near the pump motor), green corrosion on connector pins, or a connector that is not fully seated and locked. - Step 2: Diagnostic Verification
Using a scan tool, access the EBCM live data stream and monitor the Booster Temperature Sensor C PID while wiggling the harness near the connector and pump housing — erratic value jumps confirm an intermittent connection. Follow this with a multimeter check: back-probe the connector with the key off to measure resistance across the sensor terminals and compare readings against the manufacturer’s specification chart at current ambient temperature. - Step 3: Resolution & Reset Process
If resistance values fall outside spec or fluctuate during the wiggle test, replace the sensor pigtail/connector assembly or, if the thermistor is integrated into the pump module, replace the brake booster pump unit as a whole. After repair, clear the stored code using the scan tool and perform an EBCM relearn or brake bleed/calibration procedure per the platform’s service routine to confirm the stability control and ABS systems return to normal operation.
📦 Parts, Labor, and Budget Estimates
- Required Components/Software: Brake booster temperature sensor/pigtail connector (or full booster pump assembly if integrated), dielectric grease, bi-directional scan tool with EBCM reset capability
- Average Component Price: $35 – $280 USD (connector repair on the low end; full booster pump assembly replacement on the high end)
- Estimated Labor Hours: 0.8 – 2.5 hours depending on connector-only repair versus full pump replacement
- Total Estimated Budget: $150 – $550 USD