Your 8th Gen (FA5/FG2), 9th Gen (FB6/FG4), or 10th Gen (FC1/FK7) Civic may display diagnostic trouble code P0113 — which indicates a high voltage condition in the intake air temperature sensor circuit.
P0113 is defined as “Intake Air Temperature Sensor 1 Circuit High Voltage”. This code indicates that the IAT sensor circuit voltage is pegged at 4.92V or higher — which corresponds to approximately -40°F (-40°C) on the scanner.
Unlike P0111 (a logic fault), P0113 is a hard electrical failure — an open circuit. The ECU supplies a 5V reference to the IAT sensor, and the thermistor modulates voltage to ground based on air temperature. If the circuit is broken — open wire, corroded pin, failed sensor — the voltage remains at 5V and the ECU stores P0113.
Before replacing components, perform basic electrical diagnostics using a digital multimeter (DMM) and a paperclip. The following is a technical breakdown of the typical causes of P0113 on these Honda Civic models and the recommended diagnostic and repair procedures.
P0113 Diagnostic Overview: Open Circuit in IAT Sensor
P0113 (“IAT Sensor Circuit High Voltage”) is the counterpart to P0112. P0112 indicates a short to ground (low voltage), while P0113 indicates an open circuit (high voltage).
The IAT sensor is a thermistor — a resistor that changes resistance based on temperature. Cold air = high resistance = low voltage. Hot air = low resistance = high voltage.
When the ECU detects IAT sensor voltage of 4.92V or higher for at least 2.0 seconds, it stores P0113. The scanner will display a frozen -40°F (-40°C) reading, which is the default value for an open circuit.
This is not a logic fault like P0111. It is a hard electrical failure — a broken wire, corroded connector, failed sensor, or ECU issue.
Primary Failure Modes for P0113
1. Broken Harness Wire
Aftermarket intake installations or engine work may result in the sensor Wiring Harness being pulled too tight. Engine movement can flex the wires until one breaks inside the insulation, often at the connector plug.
2. Rodent Damage
Honda uses soy-based wire insulation, which is susceptible to rodent damage. Mice may chew through the ground or signal wires in the MAF/IAT harness, causing an open circuit.
3. Internal Sensor Failure
Thermal cycling can cause the internal solder joints of the IAT thermistor to crack. Once cracked, the circuit is open and the sensor has failed — replacement is required.
Platform-Specific Considerations
8th Gen (FA5/FG2, K20Z3 Si):
- Standalone sensor — threaded into the rubber intake boot between the air filter and throttle body.
- Separate sensor, inexpensive to replace.
8th Gen R18 & 9th Gen (FB6/FG4, K24Z7):
- No separate IAT sensor. It is integrated into the MAF sensor body.
- If cleaning does not resolve the issue, the entire MAF assembly must be replaced. Use OEM Denso or genuine Honda.
10th & 11th Gen Turbo (L15B7, K20C1, FC1/FK7/FL1/FL5):
- Two IAT sensors on these vehicles:
- IAT Sensor 1 — integrated into the MAF sensor housing on the airbox.
- IAT Sensor 2 — integrated into the T-MAP sensor on the charge pipe after the intercooler.
- P0113 targets IAT Sensor 1 — the one on the airbox before the turbo.
Diagnostic Procedure Using a Paperclip and DMM
This diagnostic sequence is derived from Honda’s factory service manual.
Step 1: Verify the Reading with a Scanner.
Connect a scanner with KOEO (Key On, Engine Off) and monitor IAT live data.
Evaluation: A reading of -40°F (-40°C) or 4.92V+ confirms an open circuit.
Step 2: The Paperclip Jump Test (Harness and ECU Test).
Turn the ignition OFF. Disconnect the sensor connector. Use a metal paperclip to jump the IAT signal and ground terminals on the harness side.
For standalone IAT (8th Gen Si): jump pins 1 and 2.
For integrated MAF/IAT (8th/9th Gen R18/K24, 10th/11th Gen L15B7/K20C1): jump pins 4 and 5 (IAT signal and ground) in the 5-pin MAF connector.
Turn the ignition back ON (KOEO) and monitor the scanner.
Evaluation:
- If the reading changes from -40°F to 300°F+ (or drops to 0V), the harness and ECU are functional. The sensor is faulty — replace it.
- If the reading remains at -40°F, there is an open circuit in the wiring harness. Trace the wiring back to the ECU.
Step 3: ECU Test (If the Harness Jump Fails).
If the harness jump does not change the reading, Honda’s procedure directs jumping the ECU connector terminals directly (A10 and B17 on many models) and rechecking.
Evaluation:
- If the reading changes to 300°F+, the ECU is functional — the wiring between the sensor and ECU is broken. Trace and repair the open circuit.
- If the reading remains at -40°F, the ECU may be faulty. Substitute with a known-good ECU and recheck.
OEM Part Numbers and Cost Reference
Verify fitment by VIN before ordering.
| Part | Fits | OEM Part Number | Online (RockAuto, HondaPartsNow) | Honda Dealer |
|---|---|---|---|---|
| IAT Sensor (standalone) | 8th Gen Si K20Z3 | Verify by VIN (threads into intake boot) | $15–$35 | $50–$80 |
| MAF/IAT Assembly | 8th Gen R18, 9th Gen K24Z7 | 37880-PMA-003 (verify by VIN) | $65–$110 | $150–$220 |
| MAF/IAT Sensor (IAT 1) | 10th Gen L15B7, 11th Gen L15CA | 37980-5BA-A01 (verify by VIN) | $60–$100 | $120–$180 |
| MAF/IAT Sensor (IAT 1) | 2017–2021 Civic Type R K20C1 | Verify by VIN | $70–$130 | $150–$220 |
| T-MAP Sensor (IAT 2) | 10th Gen L15B7, 11th Gen L15CA | 37830-RPY-G14 (verify by VIN) | $50–$90 | $100–$150 |
Important: On 8th/9th Gen vehicles with integrated MAF/IAT, inexpensive aftermarket sensors may not match the ECU’s expected calibration curve and can affect fuel trims. Use OEM Denso or genuine Honda components.
On 10th/11th Gen vehicles, the MAF sensor includes IAT Sensor 1. The same recommendation applies — OEM or Denso only.
Repair Cost Estimates
| Repair | DIY Cost | Independent Shop | Honda Dealer |
|---|---|---|---|
| Replace Standalone IAT Sensor (8th Gen Si) | $15–$35 | $100–$180 | $150–$250 |
| Replace MAF/IAT Assembly (8th/9th Gen) | $65–$110 (online) | $250–$400 | $350–$550 |
| Replace MAF/IAT (10th/11th Gen) | $60–$100 (online) | $180–$300 | $250–$400 |
| Wiring Repair (splice & solder) | $5–$15 (materials) | $100–$200 | $150–$300 |
| Dealer Diagnostic Fee | N/A | N/A | $120–$200 |
Pricing based on current market rates from HondaPartsNow, RockAuto, and Majestic Honda.
Pre-Purchase Inspection Note
When evaluating a used Civic with a P0113 code, the seller may state: “It just needs a sensor.”
Know the generation before purchasing:
- 8th Gen Si: Standalone IAT sensor — inexpensive ($15–$35).
- 8th Gen R18 / 9th Gen K24: IAT is integrated into the MAF — $65–$110 for the assembly. Cannot be replaced separately.
- 10th/11th Gen: IAT Sensor 1 is in the MAF on the airbox — $60–$100 online.
If the seller has not performed the basic paperclip test to verify the harness, it may indicate neglect of proper diagnostics.
Diagnostic Checklist
☐ P0113 = IAT Sensor Circuit High Voltage — open circuit, not logic fault
☐ Check IAT reading at KOEO — -40°F (-40°C) or 4.92V+ confirms open circuit
☐ Paperclip jump test — jump IAT signal and ground pins. If reading flips to 300°F+, the sensor is faulty — replace it
☐ If reading stays at -40°F after jump test — wiring has an open circuit between sensor and ECU. Trace the harness
☐ Inspect for rodent damage — Honda wiring is susceptible to rodent damage
☐ Check for broken wire at the connector — engine movement can stress the harness
☐ 8th Gen K20Z3 Si: Standalone sensor in the intake boot — $15–$35 replacement
☐ 8th Gen R18 & 9th Gen K24Z7: IAT is in the MAF assembly — $65–$110 online, cannot be replaced separately
☐ 10th/11th Gen Turbo: IAT Sensor 1 is in the MAF sensor on the airbox — P0113 targets this one
☐ 10th/11th Gen Turbo: IAT Sensor 2 is in the T-MAP on the charge pipes — not the one throwing P0113
☐ Use OEM Denso or genuine Honda for MAF/IAT assemblies — aftermarket sensors may affect fuel trims
☐ Pre-purchase inspection: Know your generation. 8th/9th Gen with integrated MAF requires more expensive replacement than standalone IAT on 8th Gen Si