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P1790 2002 Toyota Echo Code - ST Solenoid Valve Circuit Malfunction

Quick Answer

The P1790 diagnostic trouble code (DTC) for a 2002 Toyota Echo indicates a malfunction in the ST (Shift Timing) solenoid valve circuit. Common causes include Faulty ST solenoid valve, Wiring or connector issues in the ST solenoid valve circuit, Defective ECM/TCM. 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
P1790 2002 Toyota Echo indicates ST Solenoid Valve Circuit Malfunction.
Common causes
Common causes include Faulty ST solenoid valve, Wiring or connector issues in the ST solenoid valve circuit, Defective ECM/TCM.
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.
What is this?
Table of contents Created and updated by William Orellana on Sep 17, 2024
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Code P1790 2002 Toyota Echo Description

The P1790 diagnostic trouble code (DTC) for a 2002 Toyota Echo indicates a malfunction in the ST (Shift Timing) solenoid valve circuit. The ST solenoid valve is a crucial component of the transmission system that controls the timing of gear shifts. When this solenoid valve malfunctions, it can lead to issues with shifting gears smoothly and efficiently. This can result in erratic shifting patterns, harsh shifts, delayed engagement, or even the transmission getting stuck in a particular gear.

OBDII Code P1790 2002 Toyota Echo - ST Solenoid Valve Circuit Malfunction
P1790 2002 Toyota Echo Code - ST Solenoid Valve Circuit Malfunction

Common Causes of P1790 2002 Toyota Echo

  1. Faulty ST solenoid valve
  2. Wiring or connector issues in the ST solenoid valve circuit
  3. Defective ECM/TCM
  4. Low transmission fluid levels or dirty transmission fluid
  5. Electrical issues such as blown fuses or shorts in the circuit

Symptoms of P1790 2002 Toyota Echo

  1. Erratic shifting patterns
  2. Harsh shifts
  3. Delayed engagement when shifting gears
  4. Transmission getting stuck in a particular gear
  5. Illumination of the Check Engine Light

How to Fix P1790 2002 Toyota Echo

  1. Diagnose the issue by using a scan tool to retrieve the DTC and inspect the ST solenoid valve circuit for any visible damage.
  2. Test the ST solenoid valve for proper operation using a multimeter to check for continuity and resistance.
  3. Inspect the wiring and connectors in the ST solenoid valve circuit for any signs of damage or corrosion. Repair or replace as necessary.
  4. If the ST solenoid valve is faulty, replace it with a new one and ensure proper installation.
  5. Clear the DTC using a scan tool and test drive the vehicle to confirm that the issue has been resolved.

Cost to Fix P1790 2002 Toyota Echo

The cost of repairing a ST solenoid valve circuit malfunction can vary depending on the specific cause of the issue and the labor rates in your area. On average, the cost of parts for a new ST solenoid valve can range from $100 to $300, while labor costs can range from $150 to $300. Overall, you can expect to pay anywhere from $250 to $600 for this repair. Keep in mind that these are rough estimates, and actual costs may differ based on your location and the specific circumstances of your vehicle. It's recommended to consult with a professional mechanic for a more accurate cost estimate.

When is the Code Detected?

ECU memorizes DTC P1790 if (a) or (b) condition below is detected once or more, but ECU does not start MIL blinking.(a)Solenoid resistance is 30 W or lower (short circuit) when solenoid energized.(b) Solenoid resistance is 100 kW or higher (open circuit) when solenoid is not energized.

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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 P1790 2002 Toyota Echo Code

1. What are the common symptoms of OBDII code P1790 on a 2002 Toyota Echo?

Common symptoms include difficulty shifting gears, harsh shifting, or even the transmission going into limp mode.

2. What does the OBDII code P1790 on a 2002 Toyota Echo indicate?

Code P1790 indicates a malfunction in the ST Solenoid Valve circuit of the transmission.

3. What are the possible causes of the ST Solenoid Valve Circuit Malfunction in a 2002 Toyota Echo?

Possible causes include a faulty ST solenoid valve, damaged wiring or connectors in the circuit, low transmission fluid level, or a malfunctioning Transmission Control Module (TCM).

4. How can I diagnose the ST Solenoid Valve Circuit Malfunction in my 2002 Toyota Echo?

Diagnosis typically involves checking the transmission fluid level, inspecting the wiring and connectors for damage, and using a scan tool to monitor the ST solenoid valve operation.

5. Can I continue driving my 2002 Toyota Echo with OBDII code P1790 present?

It is not recommended to continue driving with P1790 as it can lead to further transmission issues. It's best to address the problem promptly.

6. How can I repair the ST Solenoid Valve Circuit Malfunction in my 2002 Toyota Echo?

Repair options may include replacing the ST solenoid valve, repairing damaged wiring or connectors, ensuring proper transmission fluid levels, or reprogramming the TCM.

7. Is it possible to reset the OBDII code P1790 on a 2002 Toyota Echo without fixing the underlying issue?

While clearing the code may temporarily turn off the check engine light, it will not solve the root problem causing the malfunction.

8. Can a DIY enthusiast fix the ST Solenoid Valve Circuit Malfunction in a 2002 Toyota Echo?

Depending on the skill level and tools available, some DIY enthusiasts may be able to address the issue themselves, but it's recommended to consult a professional for complex transmission problems.

9. How much does it cost to repair the ST Solenoid Valve Circuit Malfunction in a 2002 Toyota Echo?

Repair costs can vary based on the specific cause of the issue, but it's advisable to budget for parts and labor expenses associated with transmission repairs.

10. How often does the ST Solenoid Valve Circuit Malfunction occur in a 2002 Toyota Echo?

While not extremely common, issues with the ST solenoid valve circuit can arise in older vehicles like the 2002 Toyota Echo, especially if regular maintenance has been neglected.

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