P0727 Engine Speed Input Circuit No Signal Trouble Code

P0727 Engine Speed Input Circuit No Signal

OBD-II Trouble Code Technical Description

Engine Speed Input Circuit No Signal

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 (BMW, GMC, Chevy Duramax, Saturn, Audi, Jaguar, VW, Volvo, Kia, etc.). Although generic, the specific repair steps may vary depending on make/model.

A stored code P0727, simply means that the powertrain control module (PCM) has detected no input voltage signal from the engine speed sensor. The engine speed input sensor may also be called the transmission input speed sensor or the input speed sensor. A stored code P0727 may be caused by a mechanical problem or an electrical problem.

 

The engine speed input sensor is normally inserted through an opening in the transmission case, near the front of the input shaft and fitted with a rubber O-ring (on the sensor housing) so that it makes a seal with the transmission case. Use care when removing the sensor from the housing as hot transmission fluid may be harmful. Position a suitable container under the opening in the transmission to catch any fluid that may spill when the sensor is removed. Carefully repeat this process whenever you pan to remove any sensor from the transmission (regardless of whether you plan to test or replace it).

At the core of the typical engine input speed sensor circuit is a stationary mounted electromagnetic hall-effect sensor. It is mounted so that a toothed reluctor ring (attached to the input shaft of the transmission) passes in very close proximity to its magnetic tip. As the transmission input shaft turns, the reluctor ring spins. The raised areas of the teeth on the reluctor ring are employed to electromagnetically complete the engine speed input circuit and the recessed areas between the teeth interrupt the circuit. A waveform pattern is formed by the rapid electromagnetic completions and interruptions of the circuit. The waveform patterns represent frequency and voltage variations which the PCM recognizes as engine input speed.

A code P0727 will be stored, and a malfunction indicator lamp may be illuminated, if the PCM fails to receive engine speed input signal voltage for a set period of time and under certain circumstances. It is worth noting that 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:

P0725 Engine Speed input Circuit Malfunction P0726 Engine Speed Input Circuit Range/Performance P0728 Engine Speed Input Circuit Intermittent

Code Severity & Symptoms

A stored code P0727 should be rectified with urgency as severe transmission damage and/or drivability issues may result.

Symptoms may include:

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

Causes

Possible causes for this P0727 code include:

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

Diagnostic and Repair Procedures

A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a reliable vehicle information source, will be required to diagnose a stored code P0727 precisely.

Prior to diagnosing an automatic transmission related code (anything in the P0700s), it is a good idea to check the condition and level of the transmission fluid.

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