P1704

P1704-INPUT SPEED SENSOR 1 OVERSPEED







Theory of Operation

The NAG1 transmission has two input speed sensors 1 and 2 (N2 and N3), both speed sensors are located on the valve body. The speed sensors are hall effect speed sensors that are used by the Transmission Control Module (TCM) to calculate the transmissions input speed. Since the input speed could not be measured directly, two of the drive elements are measured. Two input speed sensors were required because both drive elements are not active in all gears.

The input speed sensors 1 and 2 will report the same input speed in gears 2nd, 3rd or 4th. If the 1 and 2 input speed sensor signals are not the same in these gears, the TCM will set the DTC P2784-Input Speed Sensor 1/2 Correlation. The input speed sensor 2 is not reported in 1st and 5th gears. The input speed sensor 1 (N2) is not reported in Reverse. The P1704-Input Speed Sensor 1 Overspeed and P1705-Input Speed Sensor 2 Overspeed DTCs are rationality checks designed to detect a major transmission failure. If either DTC is detected, the TCM will place the transmission in Neutral.

- When Monitored:
Continuously with the ignition on, engine running, transmission in gear, and Input Speed Sensor 1 (N2) greater than 0 rpm

- Set Condition:
If the RPM of the Input Speed Sensor 1 (N2) is greater than 7700 rpm.





Always perform the NAG1 Pre-Diagnostic Troubleshooting procedure before proceeding. Testing and Inspection

1. CHECK TO SEE IF DTC IS CURRENT
1. Turn the ignition on.
2. With the scan tool, erase Transmission DTCs.
3. Raise the vehicle on the hoist.
4. Start the engine.
5. With the scan tool, monitor the Input Speed Sensor 1 rpm.
6. Firmly apply the brakes and place the gear selector in Drive.

WARNING: To avoid possible serious or fatal injury, keep hands and feet clear of rotating wheels.

7. Release the brakes and raise the engine RPM to allow the transmission to upshift to the 2-3 and 3-4 shift schedule.

Did the Input Speed Sensor 1 display an rpm above 7700?

Yes

- Go To 2

No

- Go To 3

2. INTERNAL TRANSMISSION
1. This DTC is an indication of an internal transmission failure.
2. Remove the Transmission Oil Pan and inspect for excessive debris such as clutch friction material or metal contamination.

Is there any indication of an internal transmission failure?

Yes

- Repair internal transmission as necessary.
- Perform NAG1 TRANSMISSION VERIFICATION TEST. NAG1 Transmission Verification Test

No

- Using the schematics as a guide, check the Transmission Control Module (TCM) terminals for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace the TCM.
- Perform NAG1 TRANSMISSION VERIFICATION TEST. NAG1 Transmission Verification Test

3. CHECK THE WIRING AND CONNECTORS
1. The conditions necessary to set this DTC are not present at this time.
2. Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.
3. Wiggle the wiring and connectors while checking for any possible open or shorted circuits.
4. Check for any Service Information Tune-ups or Technical Service Bulletins that may apply.

Were there any problems found?

Yes

- Repair as necessary.
- Perform NAG1 TRANSMISSION VERIFICATION TEST. NAG1 Transmission Verification Test

No

- Test Complete.