Carbon buildup or mechanical binding on the secondary port throttle plate or shaft, preventing it from moving freely.; Faulty secondary port throttle actuator (motor or vacuum diaphragm, depending on the system) that fails to move the valve.; Failed secondary port throttle position sensor (TP sensor) or a wiring issue in its circuit, causing the PCM to see an incorrect position.; Open or shorted wiring, corroded connectors, or poor grounds in the secondary port throttle actuator or sensor circuits.; A stuck or leaking vacuum supply line or solenoid that controls the secondary port throttle on vacuum-operated systems.; PCM internal fault or corrupted software, though this is rare and should only be considered after all mechanical and electrical checks pass.; Intake manifold vacuum leaks or restrictions that affect the secondary port throttle's operation.

DTC codes / Chrysler codes / P1109

P1109 · ChryslerSecondary Port Throttle System

Q: What does code P1109 mean?

Secondary Port Throttle System. P1109 on Chrysler vehicles indicates a fault in the secondary port throttle system, which is the small throttle valve that controls airflow through the secondary intake port on engines with a dual-port intake manifold. The powertrain control module (PCM) monitors the secondary port throttle actuator and its position sensor, and it sets this code when the commanded position does not match the actual position or when the circuit is out of range.

P1109 on Chrysler vehicles indicates a fault in the secondary port throttle system, which is the small throttle valve that controls airflow through the secondary intake port on engines with a dual-port intake manifold. The powertrain control module (PCM) monitors the secondary port throttle actuator and its position sensor, and it sets this code when the commanded position does not match the actual position or when the circuit is out of range.

SystemPowertrain

Code typeChrysler specific

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms.
Reduced engine performance at higher engine speeds or under heavy load, where the secondary port is normally opened.
A slight hesitation or stumble during acceleration when the PCM commands the secondary port throttle to open.
Poor fuel economy or increased emissions due to incorrect airflow through the intake manifold.
In some cases, a rough idle or stalling if the secondary port throttle is stuck partially open or closed.
A noticeable lack of power above 3,000 RPM on engines that rely on the secondary port for high-speed breathing.

Common causes, most likely first

Carbon buildup or mechanical binding on the secondary port throttle plate or shaft, preventing it from moving freely.
Faulty secondary port throttle actuator (motor or vacuum diaphragm, depending on the system) that fails to move the valve.
Failed secondary port throttle position sensor (TP sensor) or a wiring issue in its circuit, causing the PCM to see an incorrect position.
Open or shorted wiring, corroded connectors, or poor grounds in the secondary port throttle actuator or sensor circuits.
A stuck or leaking vacuum supply line or solenoid that controls the secondary port throttle on vacuum-operated systems.
PCM internal fault or corrupted software, though this is rare and should only be considered after all mechanical and electrical checks pass.
Intake manifold vacuum leaks or restrictions that affect the secondary port throttle's operation.

How to diagnose and fix it

Connect a scan tool and verify the P1109 code is current, then check for any related codes and freeze-frame data to understand the conditions when the fault set.
Inspect the secondary port throttle valve for carbon buildup, sticking, or mechanical damage; clean it with intake-safe cleaner and verify it moves freely by hand.
Test the secondary port throttle actuator with a scan tool bidirectional control (if available) and observe whether the valve moves and the position sensor tracks correctly.
Check the wiring and connectors at the secondary port throttle actuator and position sensor for corrosion, chafing, or loose pins; repair as needed.
Measure resistance and voltage on the actuator and sensor circuits according to the factory service information, and compare to specifications.
On vacuum-operated systems, inspect the vacuum lines, solenoid, and reservoir for leaks or failure; replace faulty components.
If all electrical and mechanical checks pass, reflash or replace the PCM only after confirming power and ground integrity to the module.

Secondary port throttle faults often misdiagnosed

Many technicians replace the secondary port throttle actuator when the real problem is carbon buildup on the throttle plate, so always clean and verify free movement before condemning parts.
A faulty secondary port throttle position sensor can set P1109 even when the actuator works perfectly, so check sensor signal voltage and sweep with a scan tool.
On some Chrysler engines, a vacuum leak at the intake manifold gasket or a cracked vacuum line can cause the secondary port throttle to behave erratically and set this code.
P1109 can be stored intermittently due to a loose ground connection at the engine block or a chafed wire in the harness near the throttle body, so wiggle-test the harness while monitoring live data.
Do not confuse P1109 with codes for the main electronic throttle control (ETC) system; the secondary port throttle is a separate valve and requires its own diagnostic path.

Can I keep driving with P1109?

You can usually drive the vehicle with P1109 set, but avoid heavy acceleration and high-speed driving because the secondary port throttle may not open, reducing power and increasing emissions. If you notice severe hesitation, stalling, or a significant loss of power, have the vehicle inspected promptly.

Tools that help

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