What Does P0122 Mean on a 2024 Honda Civic?
A P0122 code on your 2024 Honda Civic is different from the more common P0121—it means the ECM has detected that the throttle position sensor signal has dropped below the minimum expected voltage threshold. This isn't a pattern issue; it's a circuit problem. Think of it as a detective discovering that the surveillance camera went completely dark rather than just showing fuzzy footage—the signal has dropped out entirely or fallen critically low.
The 2024 Civic uses a 2.0L naturally aspirated four-cylinder (158 hp) or a 1.5L VTEC turbocharged four-cylinder (180 hp), both with electronic throttle control. The TPS is integrated into the throttle body assembly with dual signal circuits. P0122 specifically indicates the TPS1 circuit voltage has fallen below approximately 0.2V.
Symptoms: More Severe Than P0121
- Check engine light on—may be accompanied by other TPS codes
- Significant loss of throttle response or complete throttle failure
- Engine may default to a fixed idle speed
- Severe limp mode with very limited power
- Engine may stall or refuse to accelerate
Top Causes: This Is an Electrical Issue
- Damaged or corroded throttle body connector – The connector pins can corrode, bend, or lose contact, causing the voltage to drop below threshold. This is the #1 cause of P0122. Likelihood: 35%
- Failed throttle body assembly – The internal TPS sensor has shorted or developed an open circuit, producing a below-threshold voltage. Likelihood: 30%
- Wiring harness damage – A cut, chafed, or pinched wire in the TPS circuit allows voltage to leak to ground or creates an open circuit. Likelihood: 20%
- ECM ground or reference voltage issue – The 5V reference signal from the ECM to the TPS is compromised. Likelihood: 10%
- Water intrusion – Moisture in the throttle body connector from washing or flooding. Likelihood: 5%
Estimated Repair Costs
- Connector cleaning/repair: $50–$150
- Throttle body replacement: $300–$500 parts and labor
- Wiring harness repair: $150–$350
- ECM diagnosis/repair: $200–$500+
Warranty Coverage
Your 2024 Civic is fully covered under Honda's 3-year/36,000-mile basic warranty and 5-year/60,000-mile powertrain warranty. P0122 is more urgent than P0121 due to potential throttle failure—take it to your Honda dealer immediately for no-cost repair. The dealer will use Honda Diagnostic System (HDS) to check TPS circuit voltage, reference voltage, and ground integrity.
P0122 vs. P0121: Key Differences
P0121 means the TPS signal is in range but erratic (performance issue). P0122 means the signal has dropped below minimum voltage (circuit issue). P0122 is generally more serious and more likely to require hardware replacement rather than just cleaning.
How AutoDetective AI Can Help
Upload your scan data to AutoDetective for a free diagnosis. Our AI distinguishes between TPS circuit faults (P0122) and performance issues (P0121) to guide you toward the right repair.