P1604: Throttle Actuator Control Mismatch
The P1604 code indicates that the Transmission Control Unit (TCU/TCM) has detected a discrepancy between the requested throttle angle and the actual throttle position, or has lost the ability to control the electronic throttle actuator (in models where the TCU manages traction control or rev-matching). This typically results in a limp mode with limited or no throttle response.
01. Most Common Causes
- Faulty electronic throttle body (throttle motor or internal TPS sensor)
- Open or short circuit in wiring or connectors between TCU, ECM, and throttle body
- CAN Bus communication failure between ECM and TCU
- Defective TCU/TCM (damaged internal driver)
- Faulty ECM (does not send correct torque demand signal)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine power or limp mode
- Poor acceleration or no throttle response
- Harsh or delayed shifting
- Transmission may not shift properly
03. Step-by-Step Diagnosis
Scan for codes and verify P1604 is present; check for related codes (e.g., throttle position sensor, CAN bus).
Inspect throttle body wiring and connectors for damage, corrosion, or loose connections.
Test throttle body operation using a scan tool to command throttle opening and compare actual vs. requested angle.
Check CAN bus communication between ECM and TCU using an oscilloscope or scan tool.
If wiring and communication are OK, suspect faulty throttle body, TCU, or ECM; perform component tests per manufacturer procedures.
1. Frequently Asked Questions
Is it safe to drive?▼
No, it is not safe to drive. The vehicle may enter limp mode with severely reduced power, increasing the risk of accidents, especially in traffic or on highways.
How much does it cost to fix?▼
Repair costs vary widely: throttle body replacement $200-$600, TCU replacement $500-$1500, ECM replacement $500-$2000, plus diagnostic fees $100-$200. Total can range from $300 to $2500+ depending on the root cause.