AutoCodes – Lexus – P1120 Lexus

P1120 Lexus Code - Coolant Flow Control Valve Position Sensor Circuit

Quick Answer

This system uses an electric pump to supply hot coolant stored in the heat storage tank into the cylinder head of the engine, in order to optimize engine starting combustion and reduce the amount of unburned gas that is discharged while the engine is started. Common causes include Coolant Flow Control Valve, Faulty Coolant Flow Control Valve Position Sensor, Coolant Flow Control Valve Position Sensor harness is open or shorted. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P1120 Lexus indicates Coolant Flow Control Valve Position Sensor Circuit.
Common causes: Common causes include Coolant Flow Control Valve, Faulty Coolant Flow Control Valve Position Sensor, Coolant Flow Control Valve Position Sensor harness is open or shorted.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 7,503

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Dec 10, 2021

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P1120 Lexus Description

This system uses an electric pump to supply hot coolant stored in the heat storage tank into the cylinder head of the engine, in order to optimize engine starting combustion and reduce the amount of unburned gas that is discharged while the engine is started. Before the engine starts, the Engine Control Module (ECM) operates the electric water pump to direct the hot coolant in the heat storage tank into the engine, in order to heat the cylinder head (this process is called preheat mode). The duration of the operation of the electric water pump is variable, depending on the temperature of the cylinder head. During the normal operation of the engine, the water valve opens the passage between the cylinder head and the heater and closes the passage between the cylinder head and the tank. During preheat mode in which the cylinder head is heated, the water valve opens the passage between the tank and the cylinder head, in order to allow the coolant to flow from the tank to the cylinder head. At this time, in order to warm up the intake port quickly before the engine is started, the coolant flows in the reverse direction.
The water valve for the Coolant Heat Storage (CHS) system, which is located at the heater hoses, controls the coolant passages to the engine, heater core, and the CHS tank in accordance with the operating conditions of the system.
The water valve consists of a water valve, valve position sensor, and valve control motor. The potentiometer, which is coupled coaxially to the water valve, converts the valve position into voltage and transmits it to the ECM in the form of a position signal.

OBDII Code P1120 Lexus - Coolant Flow Control Valve Position Sensor Circuit - AutoCodes.com — P1120 Lexus Code - Coolant Flow Control Valve Position Sensor Circuit

What does this mean?

What are the Possible Causes of the DTC P1120 Lexus?

Coolant Flow Control Valve
Faulty Coolant Flow Control Valve Position Sensor
Coolant Flow Control Valve Position Sensor harness is open or shorted
Coolant Flow Control Valve Position Sensor circuit poor electrical connection
Faulty Engine Control Module (ECM)

How to Fix the DTC P1120 Lexus?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code Tech Notes

For Non-Hybrid Lexus Vehicles P1120 = Accelerator Pedal Position Sensor Circuit Malfunction. See: P1120 Lexus

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P1120 Lexus code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P1120 Lexus code?

Need more information on how to fix the P1120 Lexus code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P1120 Lexus code diagnosed by a professional: Find a repair shop in your area

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P1120 Lexus Code

What does the OBDII code P1120 mean for a Lexus?

P1120 indicates an issue with the Coolant Flow Control Valve Position Sensor Circuit, which monitors the position of the coolant flow control valve in the engine.

What are the common symptoms of code P1120 in a Lexus?

Symptoms may include the check engine light turning on, engine overheating, reduced heater performance, or erratic engine temperature readings.

What causes code P1120 on a Lexus?

Common causes include a faulty coolant flow control valve, damaged position sensor wiring, corroded electrical connections, or a malfunctioning engine control module (ECM).

Can code P1120 cause engine damage?

If left unresolved, P1120 can lead to improper coolant flow, causing overheating and potential engine damage over time.

How can I diagnose code P1120 on a Lexus?

Diagnosis typically involves inspecting the coolant flow control valve, testing the position sensor, checking wiring for damage or corrosion, and using a scan tool to monitor sensor readings.

What tools are needed to fix code P1120?

You may need a scan tool, multimeter, basic hand tools, and potentially a replacement coolant flow control valve or position sensor.

Is it safe to drive a Lexus with code P1120?

It’s not recommended to drive long distances with this code active, as it may result in overheating or damage to the engine.

How much does it cost to repair code P1120 on a Lexus?

Repair costs can range from $150 to $500, depending on whether the coolant flow control valve, sensor, or wiring needs replacement.

Can I fix code P1120 myself on a Lexus?

If you have basic automotive repair skills, you can inspect the valve and wiring, but replacing the control valve or sensor may require professional assistance.

What preventive measures can help avoid code P1120?

Regular maintenance, such as inspecting coolant system components for wear or damage and ensuring clean electrical connections, can help prevent this code.

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