P1602 — Throttle Control Unit Modulated Command Malfunction

P1602 — Throttle Control Unit Modulated Command Malfunction. A fault in the throttle and intake air metering. Short, gentle driving to a shop is usually possible. Typical causes: failed electronic throttle motor, wiring or connector faults in the throttle circuit, intake air leaks after the MAF sensor.

For Ford vehicles

immobiliser - engine control unit communication

powertrain (engine/transmission)

Is it safe to drive?

Drive with caution Drive with caution. Many throttle faults put the car into limp mode with limited power — enough to reach a shop, not for highway trips. If the engine stalls or the pedal stops responding, do not drive.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm P1602 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the throttle and intake air metering for damage, corrosion, chafing or poor contact.
Subsystem check Run the module's actuator test for the throttle control unit modulated command if your scanner supports it — a component that does not respond to a direct command is confirmed faulty.
Subsystem check Inspect and clean the throttle body; check that the plate moves freely.
Subsystem check Watch throttle position and MAF/MAP readings in live data while pressing the pedal — values should change smoothly.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P1602 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for P1602 (parts and labor, USD, independent shop rates): Clean the throttle body: $80–$200; Replace the throttle body assembly: $250–$700; Replace the MAF or MAP sensor: $150–$400. Overall, fixing P1602 usually costs between $80 and $700. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

What is the most common cause of P1602?

The most common causes are: failed electronic throttle motor, wiring or connector faults in the throttle circuit, intake air leaks after the MAF sensor.

What does OBD2 code P1602 mean?

How do I diagnose P1602 myself?

Start with a scan: confirm P1602, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the throttle control unit modulated command, and verify the suspect component against live data before buying parts.

What are the symptoms of P1602?

Drivers most often notice: unstable or high idle, poor throttle response, limp-home mode with reduced power, Check Engine Light on.

How much does it cost to fix P1602?

Clean the throttle body — $80–$200; Replace the throttle body assembly — $250–$700; Replace the MAF or MAP sensor — $150–$400. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

When your engine control unit detects a problem with the throttle and intake air metering system, it may store trouble code P1602. This code indicates that the module's self-diagnostics have flagged an abnormality in the throttle control unit's modulated command — essentially, the computer is telling you it cannot reliably control or verify the throttle's operation. The P in the code designation places this squarely in the powertrain category, meaning it affects the engine and transmission management systems.

The throttle control system relies on precise electronic commands to regulate airflow into the engine. When you press the accelerator pedal, sensors relay your intention to the ECU, which then commands the throttle actuator to open or close accordingly. The module continuously verifies these commands through internal self-tests. If those tests fail — meaning the actual throttle behavior doesn't match what the ECU expected to see — P1602 gets set. This isn't a simple electrical open or short circuit; the fault can originate from the control module itself, the throttle actuator, supporting sensors, or the wiring between them. The code only triggers after the problematic condition occurs multiple times under specific driving circumstances, which is why the freeze frame data stored alongside P1602 is so valuable — it shows exactly what the engine was doing when the failure was detected.

Common Symptoms of P1602

P1602 affects how your engine responds to driver input, and symptoms reflect that compromised throttle control:

Illuminated Check Engine light that remains on after a brief drive
Erratic or unusually high idle speed that fluctuates without driver input
Noticeably delayed or sluggish throttle response when pressing the accelerator
Activation of reduced-power limp-home mode, limiting acceleration and speed
Engine stalling when decelerating to a stop or at low speeds

What Causes P1602

This fault can stem from several sources within the throttle and air metering system. In many cases, the root cause is simpler than the code might suggest:

Dirty or carbon-fouled throttle body causing the plate to stick or move sluggishly
Wiring or connector problems in the throttle control circuit, including corroded terminals or chafed insulation
Internal failure of the throttle control unit's modulated command function itself
Faulty throttle position sensor or accelerator pedal position sensor sending incorrect data
Contaminated or malfunctioning MAF (mass airflow) or MAP (manifold absolute pressure) sensor
Software or driver fault within the engine control module

How to Diagnose P1602

A systematic approach prevents unnecessary parts replacement. Follow these steps in order:

Connect an OBD2 scanner and confirm P1602 is currently stored. Record all freeze frame data — this snapshot of engine load, RPM, coolant temperature, and vehicle speed tells you the exact conditions present when the fault occurred.
Check for additional diagnostic trouble codes. Related codes often point directly to the failing component. Search for applicable Technical Service Bulletins for your specific make and model, as manufacturers frequently issue software updates or known-fix documentation for common P0xxx codes.
Perform a visual inspection of the throttle body wiring harness and electrical connectors. Look for damaged wires, corrosion, loose connections, or evidence of heat damage that could interrupt signals between the ECU and throttle actuator.
If your scan tool supports bidirectional controls, run the module's actuator test for the throttle control. A properly functioning throttle will respond to direct commands; one that ignores these commands is confirmed faulty.
Remove and inspect the throttle body. Clean carbon deposits from the throttle plate and bore using appropriate throttle body cleaner. Verify the plate opens and closes freely without binding.
Monitor live data streams for throttle position sensor and MAF/MAP sensor readings while gradually pressing the accelerator. Values should change smoothly and proportionally — erratic jumps or flatlined readings indicate sensor failure.

Repair Options and Costs

Begin with the least expensive repairs before considering component replacement. All prices reflect typical parts and labor at independent repair shops in USD:

Throttle body cleaning service: $80–$200
Throttle body assembly replacement: $250–$700
MAF or MAP sensor replacement: $150–$400

The overall cost to resolve P1602 typically falls between $80 and $700 depending on which component requires attention. An accurate diagnosis before purchasing parts is essential — the most expensive repair scenarios should be investigated last.

Can You Drive With P1602?

Drive with caution. Throttle control failures frequently trigger limp-home mode, which restricts engine power to prevent potential safety issues. This reduced-power state allows you to reach a repair facility safely, but aggressive driving or highway travel is not recommended. If you experience complete throttle unresponsiveness or the engine stalls without warning, stop driving immediately and have the vehicle towed.