🚨 Diagnostic Profile
Vehicle Make: BUICK
Technical Description: (Alternative Fuel) Gas Mass Sensor Circuit High Frequency
This diagnostic trouble code indicates that the Engine Control Module (ECM) has detected an abnormally high frequency signal from the gas mass (fuel composition/flow) sensor circuit used in alternative fuel system monitoring. This sensor measures the mass flow rate of gaseous fuel (such as CNG or LPG) to help the ECM calculate proper fuel delivery and air-fuel ratio calibration. A high frequency reading typically points to a wiring issue, sensor malfunction, or signal interference rather than a mechanical fuel delivery problem.
🚨 Repair Difficulty Tier
Difficulty Rating: Intermediate
This repair requires a capable OBD-II scan tool with live data streaming capability and a digital multimeter to properly test circuit voltage, frequency output, and signal integrity. While no airbag or restraint system risk is involved, the alternative fuel system components require careful handling due to pressurized gas lines and the need for accurate sensor calibration. A technician with moderate electrical diagnostic experience and familiarity with alternative fuel systems should be able to complete this repair, though dealer-level scan tools may be needed for full system verification on certain Buick alternative fuel platforms.
🛠️ Resolution Steps
Step 1: Preliminary Inspection
Begin by visually inspecting the gas mass sensor and its wiring harness for signs of damage, corrosion, or loose connections. Check the connector pins for bent or pushed-out terminals, and inspect the wiring for chafing, pinches, or exposure to excessive heat near the engine bay. Confirm that the sensor is securely mounted and that there is no visible contamination or debris affecting the sensor’s internal mass flow measurement element. Also inspect the ground strap connections near the ECM and sensor circuit, as poor grounding is a common cause of erratic frequency signals.
Step 2: Diagnostic Verification
Connect an OBD-II scan tool capable of reading manufacturer-specific live data and monitor the gas mass sensor’s frequency output in real time. Compare the live frequency reading against the manufacturer’s specified normal operating range at idle and under light acceleration. Using a digital multimeter, probe the sensor’s signal wire at the connector (with the key on, engine off, and then running) to confirm consistent frequency output rather than erratic spikes. Additionally, test the sensor’s reference voltage and ground circuit to rule out a wiring-related issue before condemning the sensor itself. If frequency readings remain abnormally high despite proper wiring, the sensor is likely at fault.
Step 3: Resolution & Reset Process
If wiring and connections test correctly but the sensor output remains out of range, replace the gas mass sensor with an OEM-specified replacement unit. After installation, clear the stored diagnostic trouble codes using the scan tool and perform a key-cycle relearn procedure if required by the vehicle’s alternative fuel module. Road test the vehicle while monitoring live sensor data to confirm the frequency signal now falls within the normal operating parameters and that no additional codes return after a full drive cycle.
📦 Parts, Labor, and Budget Estimates
Required Components/Software: Gas mass (fuel flow) sensor, sensor wiring harness connector (if damaged), OBD-II scan tool with manufacturer-specific live data access, digital multimeter, and possible dealer-level diagnostic software for relearn procedures on alternative fuel modules.
Average Component Price: $120 – $320 for the gas mass sensor itself; wiring harness repairs typically range from $40 – $150 depending on harness section length and connector availability; dealer programming or relearn procedures (if required) may range from $80 – $150.
Estimated Labor Hours: 1.0 to 2.0 hours for diagnosis, testing, and sensor replacement; an additional 0.5 hours may be required if wiring repair or module relearn procedures are necessary.