P1704 Input speed sensor 1 overspeed

P1704 code - The NAG1 transmission has two input speed sensor 1 and 2 (N2 and N3), both speed sensors are located on the valve body. The speed sensors are hall effect speed sensor that are used by the transmission control module (TCM) to calculate the transmission input speed. since the input speed could not be measured directly, two of drive elements are measured. Two input speed sensors were required because both drive elements are not active in all gears. The input speed sensor 1 overspeed and P1705 input speed sensor 2 overspeed DTCs are rationality checks designed to detect a major transmission failur. If either DTC is detected, the TCM will place the transmission in neutral.

When monitored this DTC 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.

Possible causes P1704 code:

- Internal transmission 

- Transmission control module (TCM)

Diagnostic test P1704 code

Step 1. Check to see if DTC is current

Turn the ignition on. With the scan tool, erase transmission DTCs. Raise the vehicle on the hoist. Start the engine. With the scan tool, monitor the input speed sensor 1 rpm. Firm apply the brakes and place the gear selector in drive. To avoid serious or fatal injury, keep hands and feet clear of rotating wheels. 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 step 2.

No, go to step 3.

Step 2. Internal transmission

This is an indication of an internal transmission failure. Remove the transmission oil pan 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 in accordance with the service information. Perform 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 in accordance with the service information. Perform NAG1 Transmission Verification Test. 

Step 3. Check the wiring and connectors

The conditions necessary to set this DTC are not present at this time. Using the schematics as a guide, inspect the wiring and connectors specific to this circuit. Wiggle the wiring and connectors while checking for any possible open or shorted circuits. 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. 

No, test complete.

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