AutoCodes – Toyota – P1123 2008 Toyota Prius

P1123 2008 Toyota Prius Code - Coolant Flow Control Valve Position Sensor Circuit High

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
P1123 2008 Toyota Prius indicates Coolant Flow Control Valve Position Sensor Circuit High.
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.
AI answers can be wrong. Verify repairs with testing. Open full chat
Code Popularity 7,250
How popular is this code, among other codes? Low
Table of contents Created and updated by William Orellana on May 12, 2024
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Code P1123 2008 Toyota Prius 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 P1123 2008 Toyota Prius - Coolant Flow Control Valve Position Sensor Circuit High - AutoCodes.com
P1123 2008 Toyota Prius Code - Coolant Flow Control Valve Position Sensor Circuit High

What are the Possible Causes of the DTC P1123 2008 Toyota Prius?

  • 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 P1123 2008 Toyota Prius?

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 is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P1123 2008 Toyota Prius 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 P1123 2008 Toyota Prius code?

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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 P1123 2008 Toyota Prius Code

1. What does the OBDII code P1123 mean on a 2008 Toyota Prius?

P1123 indicates a problem with the Coolant Flow Control Valve Position Sensor Circuit, specifically a high voltage issue.

2. What are the symptoms of code P1123 in a 2008 Toyota Prius?

Common symptoms include the check engine light turning on, reduced heating efficiency in the cabin, or the engine running hotter than normal.

3. What causes the P1123 code to appear in a 2008 Toyota Prius?

Typical causes include a faulty coolant flow control valve, damaged wiring or connectors in the circuit, or a malfunctioning position sensor.

4. Can I still drive my 2008 Toyota Prius with the P1123 code?

While the car may still be drivable, ignoring this code can lead to inefficient engine cooling and potential overheating, which could cause further damage.

5. How do I diagnose the P1123 code on a 2008 Toyota Prius?

Start by inspecting the coolant flow control valve, wiring, and connectors for damage. Use a multimeter to check for voltage and continuity in the circuit.

6. How can I fix the P1123 code on my 2008 Toyota Prius?

Repairs may involve replacing the coolant flow control valve, repairing or replacing damaged wiring, or addressing any issues with the position sensor.

7. Does the P1123 code affect fuel efficiency in a 2008 Toyota Prius?

Yes, a malfunctioning coolant flow control valve can reduce engine efficiency and potentially impact fuel economy.

8. How much does it cost to repair a P1123 code on a 2008 Toyota Prius?

The cost varies but typically ranges from $200 to $500, including parts and labor, depending on whether the valve or wiring needs replacement.

9. Can a low coolant level trigger the P1123 code on a 2008 Toyota Prius?

While uncommon, low coolant levels could lead to overheating issues, indirectly affecting the coolant flow control valve's operation.

10. Is the P1123 code common in 2008 Toyota Prius vehicles?

This code is not extremely common but can appear in older Prius models due to wear and tear on the coolant flow control valve and related components.

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