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Tramission repair

(1999 Ford Contour)
in Hampton, VA on December 11, 2009
I have Actron code reader that pulled up code P0708 from computer (tranmission range sensor curcuit has high input). Any help on troubleshooting this?
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on December 11, 2009
Customer Concern: Transmission intermittently shifts erratically, or comes out of gear. Has a code P0708 in memory for high Transmission Range (TR) sensor input.
Tests/Procedures: 1. Check the Brown/Light Green wire at the TR sensor for a good ground while wiggling and tugging on the wiring harness.

2. If the ground is OK, monitor the voltage on the White/Light Green wire at the TR sensor. With the TR sensor disconnected, the voltage on this wire should be 5 volts, which comes from the Powertrain Control Module (PCM). With the TR sensor connected, the voltage should be 4.4 volts with the shift lever in park, 3.6 volts in reverse, 2.8 volts in neutral, 2.1 volts in drive, 1.4 volts in manual 2nd, and 0.7 volts in manual 1st (all readings can be +/- 0.2 volts and still be acceptable). Tap the sensor and "wiggle" the shifter while monitoring the voltage.

3. If the unplugged reading is OK, but the plugged-in readings are incorrect or erratic, replace the TR sensor.
Potential Causes: Defective TR Sensor

Tech Tips: If the TR sensor voltage is inconsistent or erratic, it can cause the PCM to unexpectedly downshift the transmission, which can feel like the transmission went into neutral.
Diagnostic Codes: P0708

Customer Concern: After driving 15 miles, the engine RPM will flare or decrease. Flare is 2K RPM, decrease is 600 RPM and then returns to a steady state. When it returns to normal, it feels like being hit with sledgehammer. Slowing down or braking does not stop the jerking, nor does powering the engine. This continues until shutdown and cooled off. No check engine light and only 1 code 1 time of P0708.
Tests/Procedures: 1. Using a digital voltmeter, backprobe the White/Green wire at Powertrain Control Module (PCM) pin 64. Road test the vehicle while monitoring the Transmission Range (TR) voltage for being stable. If the voltage varies drastically while the symptom is occurring, replace the TR sensor and recheck for proper operation.
NOTE: If the PCM sees the voltage change, it 'assumes' the shifter has been moved to a different position and will control the solenoids to cause either an upshift or downshift based on the voltage seen.
Potential Causes: Transmission Range (TR) Sensor
Transmission Range (TR) Sensor Connector
Transmission Range (TR) Sensor Wiring

Tech Tips: The TR sensor is an input to the PCM to inform it of the gear selected. This value is used to control the transmission solenoids for proper shifting. Expected values are: P) 4.4 volts R) 3.6 volts N) 2.9 volts D) 2.0 volts 2) 1.4 volts 1) 0.7 volts
Diagnostic Codes: P0708

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