Faulty throttle vent control motor (winding open or shorted).; Damaged or corroded wiring harness in the throttle vent control motor circuit 2.; Loose or corroded electrical connector at the throttle body or PCM.; Failed throttle body assembly due to internal wear or contamination.; PCM internal driver failure for circuit 2 (rare but possible).; Aftermarket or incorrect throttle body installation causing signal mismatch.; Carbon buildup or mechanical binding in the throttle vent mechanism.

DTC codes / Honda codes / P1242

P1242 · HondaThrottle Vent Control Motor Circuit 2 Malfunction

Q: What does code P1242 mean?

Throttle Vent Control Motor Circuit 2 Malfunction. P1242 on Honda vehicles indicates that the powertrain control module (PCM) has detected an electrical fault in the throttle vent control motor circuit, specifically circuit 2. The PCM monitors the current and voltage on this circuit and sets the code when the signal falls outside the expected range, often due to an open, short, or excessive resistance in the wiring or motor.

P1242 on Honda vehicles indicates that the powertrain control module (PCM) has detected an electrical fault in the throttle vent control motor circuit, specifically circuit 2. The PCM monitors the current and voltage on this circuit and sets the code when the signal falls outside the expected range, often due to an open, short, or excessive resistance in the wiring or motor.

SystemPowertrain

Code typeHonda specific

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering (injector circuits)

Symptoms you may notice

Illumination of the check engine light or malfunction indicator lamp (MIL).
Often no symptoms besides the warning light, especially if the vent motor is not critical for normal driving.
Rough idle or unstable engine speed due to improper throttle venting.
Reduced engine performance or limp mode in some cases.
A buzzing or clicking noise from the throttle body area after engine shutdown.
Poor fuel economy or hesitation during acceleration.

Common causes, most likely first

Faulty throttle vent control motor (winding open or shorted).
Damaged or corroded wiring harness in the throttle vent control motor circuit 2.
Loose or corroded electrical connector at the throttle body or PCM.
Failed throttle body assembly due to internal wear or contamination.
PCM internal driver failure for circuit 2 (rare but possible).
Aftermarket or incorrect throttle body installation causing signal mismatch.
Carbon buildup or mechanical binding in the throttle vent mechanism.

How to diagnose and fix it

Inspect the throttle body connector and wiring for corrosion, chafing, or loose pins; clean and secure as needed.
Measure resistance of the throttle vent control motor circuit 2 at the motor terminals and compare to Honda specifications.
Check for continuity and short-to-ground or short-to-power on the circuit 2 wiring between the throttle body and PCM.
Test the throttle vent control motor by applying battery voltage briefly to confirm operation (if accessible and safe).
Replace the throttle body assembly if the motor or internal circuit is faulty, then perform a PCM idle relearn or throttle body calibration.
If wiring and motor test good, diagnose the PCM driver circuit and replace PCM only after confirming all other possibilities.
Clear the code and verify repair by performing a road test and monitoring live data for the throttle vent control motor circuit.

Common Misdiagnosis Traps for P1242

A dirty throttle body often causes P1242 because carbon buildup restricts the vent motor, leading to excessive current draw that the PCM interprets as a circuit fault.
Many technicians replace the throttle body unnecessarily when the real issue is a corroded connector pin or a chafed wire in the harness near the intake manifold.
P1242 can be set by a weak battery or charging system issue that causes voltage spikes, so always check battery health and ground connections first.
On some Honda models, a faulty PCM relay or poor ground can mimic a circuit 2 failure, so verify power and ground at the PCM before condemning the module.
After replacing the throttle body, failing to perform the idle relearn procedure can cause the code to reappear immediately, leading to a false comeback.

Can I keep driving with P1242?

You can usually drive the vehicle with P1242, but avoid aggressive acceleration and prolonged idling until repaired. If the engine enters limp mode or runs poorly, seek service promptly to prevent further damage.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for Honda vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.