Mechanics

JAGUAR 420G ENGINE PROBLEM

1996 Jaguar 420G • 138,000 miles

Have code p0727 which put car in Limp mode; Explanation is that the engine speed input circuit no signal-P0727.
Checked all wiring form and to TCM, ECM all are fine. Just removed trans cover to check speed sensor ut it is part of the harness.
please help
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November 3, 2012.




ENGINE SPEED INPUT - P0726/P0727
The engine speed input signal is a square wave output from the ECM. The signal is 12 volt active high with a duty cycle of 50 /120 of crankshaft revolution i.E. 3 pulses per revolution. The frequency of the signal is proportional to engine speed.

Engine Speed Input Circuit - Range/Performance P0726
Engine speed is continuously monitored by the background diagnostics. This fault is flagged if the engine speed exceeds the maximum speed threshold (approx 6800 rpm). This fault code would suggest an intermittent fault in the circuit.

Engine Speed Input Circuit No Signal - P0727
If the engine speed drops below 95 rpm and the selected gear is not P or N, then the TCM will initiate the default mode. This fault code will only be stored if the output speed is greater than 300 rpm. This is to prevent spurious flagging of codes if the engine stalls.

Possible Causes : Faulty harness wiring 1 connectors.
Faulty signal from ECM.

Effects : MIL illuminated.
Transmission warning lamp illuminated.
Maximum fluid pressure applied.
Limp home mode applied.

Remedy : Repair or renew harness 1 connectors.
Examine ECM fault diagnosis.

Troubleshooting Schematic

Key To Schematic Diagrams

Transmission Control Module (TCM)
Transmission Unit
TCM Multi-pin Connector
Transmission Rotary Switch
Transmission Connector Plug
Engine Control Module
Instrument Pack
ABS/Traction Control Control Module
Kickdown Switch



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