P0725 Engine Speed input Circuit Malfunction Trouble Code

P0725 Engine Speed Input Circuit Malfunction

OBD-II Trouble Code Technical Description

Engine Speed Input Circuit Malfunction

What does that mean?

This diagnostic trouble code (DTC) is a generic powertrain code, which means that it applies to all OBD-II equipped vehicles (Nissan, Dodge, VW, Jeep, Mazda, Honda, Chrysler, Subaru, etc.). Although generic, the specific repair steps may vary depending on make/model.

The presence of a stored code P0725 means that the powertrain control module (PCM) has detected a circuit malfunction with the engine speed sensor input signal. The engine speed input sensor is sometimes called the transmission input speed sensor and the input speed sensor. This type of code may be caused by a mechanical problem or an electrical problem.

 

The engine speed input speed sensor is usually inserted through the transmission case, near the front of the input shaft. Typically, a rubber O-ring is fitted onto the sensor housing so that the sensor makes a seal with the transmission case. Use caution when removing the sensor from the housing as hot transmission fluid may be harmful. Place a suitable container under the opening in the transmission to catch any fluid that may pour out when the sensor is removed (for testing or replacement).

The basic theory of operation of an engine input speed sensor circuit is that an electromagnetic hall-effect sensor is mounted in such a manner as to allow a toothed reluctor ring to pass in very close proximity to its magnetic tip. The reluctor ring is mechanically affixed to the input shaft of the transmission so that when the shaft spins, it spins in conjunction. The raised areas of the teeth serve to electromagnetically complete the engine speed input circuit while the recessed areas between the teeth interrupt the circuit. These rapid completions/interruptions form an electronic waveform pattern that represents a particular frequency and degree of voltage. The waveform pattern is recognized by the PCM as engine input speed.

If the PCM fails to recognize the appropriate engine speed input signal, for a set period of time and under certain circumstances, a P0725 will be stored and a malfunction indicator lamp may be illuminated.

Unacceptable engine speed input signals may include excessive voltage, insufficient voltage, or incorrect voltage as compared to transmission output speed, throttle position, or engine RPM. In some cases, the transmission control module (TCM) or PCM may enter limp-in mode when this code is stored.

Related engine speed input circuit engine codes include:

P0726 Engine Speed Input Circuit Range/Performance P0727 Engine Speed Input Circuit No Signal P0728 Engine Speed Input Circuit Intermittent

Code Severity & Symptoms

A stored code P0725 should be considered severe as the conditions which have caused it to be stored may result in damage to the transmission.

Symptoms may include:

Erratic or inoperative speedometer/odometer Automatic transmissions may shift harshly (limp-in mode) Transmission fails to shift or shifts erratically Inoperative or incorrect tachometer Transmission slippage or delayed engagement Additional transmission input/output speed codes may be stored

Causes

Possible causes for this P0725 code include:

Defective engine speed input sensor or transmission output speed sensor Damaged or worn engine speed sensor reluctor ring Open or shorted wiring and/or connectors in the engine speed input circuit Excessive metal deposits on the magnetic tip of the sensor in question Mechanical transmission failure which results in transmission/clutch slippage

Diagnostic and Repair Procedures

In order to diagnose a P0725, I would need access to a diagnostic scanner, a digital volt/ohmmeter (DVOM), and a reliable vehicle information source.

When diagnosing an automatic transmission related code (a

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