A 2001 Ford Focus experiencing erratic shifting, power loss, and a P1120 OBD2 code points towards a potential issue with the throttle position sensor (TPS). Replacing the TPS is a common first step, but as one driver discovered, the problem may not always be that simple. This article explores a real-world scenario of a 2001 Ford Focus with a P1120 code and persistent issues even after TPS replacement.
Beyond the TPS: When P1120 Persists
A driver reported experiencing delayed and jerky shifting between gears, disengagement between 2nd and 3rd gear, decreased acceleration, and engine stalling at low speeds. These symptoms coincided with a P1120 diagnostic trouble code (DTC), indicating a problem with the throttle position sensor circuit. Following the code’s suggestion, the driver replaced the TPS. However, the original symptoms remained, and the P1120 code reappeared after a short period of driving. The vehicle continued to stall at low speeds without warning.
Seeking Professional Help: Mechanic and Transmission Specialist
After the unsuccessful TPS replacement, the vehicle was taken to a general mechanic. Unable to pinpoint the issue, the mechanic referred the driver to a transmission specialist. The transmission specialist, after inspection, couldn’t find any faults with the transmission itself. The car was returned to the original mechanic for further diagnosis. This highlights the complexity of diagnosing intermittent car problems, even for experienced professionals.
Exploring Other Potential Causes
While the P1120 code directly implicates the TPS, the persistence of the problem after replacement suggests other potential culprits. Further diagnostics may be necessary to investigate these possibilities:
- Wiring and Connectors: Damaged or corroded wiring and connectors in the TPS circuit can disrupt signal transmission, causing the P1120 code and related symptoms.
- PCM (Powertrain Control Module): In rare cases, a faulty PCM can misinterpret signals or fail to control the throttle properly, leading to the observed issues.
- Vacuum Leaks: Unmetered air entering the engine can disrupt the air-fuel mixture and cause erratic engine behavior, potentially contributing to the stalling and shifting problems.
- Idle Air Control Valve (IAC): A malfunctioning IAC valve can disrupt idle speed and contribute to stalling at low speeds.
Conclusion: The P1120 Puzzle
The case of the 2001 Ford Focus with a persistent P1120 code demonstrates that troubleshooting car problems can be a complex process. While the OBD2 code provides a starting point, it’s not always a straightforward solution. When a code persists after replacing the indicated part, further diagnostics are crucial to explore related components and underlying issues. A thorough inspection of wiring, connectors, and other potential culprits, like the PCM, vacuum leaks or the IAC valve, is often necessary to pinpoint the root cause and restore proper vehicle function.
