Circuit Description
The Automatic Transmission Input (Shaft) Speed (A/T ISS) Sensor provides transmission input speed to the Vehicle Control Module (VCM). The A/T ISS Sensor is a Permanent Magnet (PM) generator. The sensor mounts into the transmission case and maintains a slight air gap between the sensor and the Forward Clutch Housing. The PM generator produces an AC voltage as the Forward Clutch Housing rotor teeth pass through the sensor's magnetic field. The AC voltage level increases as the turbine shaft speed increases. The VCM converts the AC voltage into a digital signal. The VCM determines actual turbine speed using the digital signal. The VCM uses the input speed to calculate torque converter slip speed, and gear ratios.
When the VCM detects a low or no input speed during high vehicle and high engine speeds, then DTC P0717 sets. DTC P0717 is a type D DTC. For California emissions vehicles, DTC P0717 is a type B DTC.
Conditions for Setting the DTC
| • | No OSS DTC P0502 or P0503. |
| • | No TFP Val. Position Sw. DTC P1810. |
| • | TFP Val. Position Switch is not Park or Neutral. |
| • | The vehicle speed is greater than 12 mph. |
| • | The engine runs greater than 475 RPM for at least 5 seconds. |
| • | The measured input speed is less than 25 RPM for at least 5.0 seconds. |
Action Taken When the DTC Sets
| • | For California emissions only, the VCM illuminates the Malfunction Indicator Lamp (MIL). |
| • | The VCM defaults the transmission to maximum line pressure. |
| • | The VCM freezes shift adapts. |
| • | DTC P0717 is stored in VCM history. |
Conditions for Clearing the MIL/DTC
| • | For California Emissions, the VCM turns OFF the MIL after three consecutive ignition cycles without a failure reported. |
| • | A scan tool can clear the DTC from the VCM history. The VCM clears the DTC from the VCM history if the vehicle completes 40 warm-up cycles without a failure reported. |
| • | The VCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the VCM. |
Diagnostic Aids
| • | Inspect the wiring at the VCM , the Output Shaft Speed (OSS) Sensor connector and all other circuit connecting points for the following: |
| - | A bent terminal |
| - | A backed out terminal |
| - | A damaged terminal |
| - | Poor terminal tension |
| - | A chafed wire |
| - | A broken wire inside the insulation |
| - | Moisture intrusion |
| - | Corrosion |
| - | The A/T ISS sensor harness being near the DIS components or the ignition wires. |
| • | When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change. |
| • | First diagnose and clear any engine DTCs or TP Sensor codes that are present. Then inspect for any transmission DTCs that may have reset. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests for proper operation to the A/T ISS Sensor.
-
This step tests for proper A/T ISS circuit operation up to the VCM connections. Remove the fuel pump relay in order to eliminate a flooding condition during this step.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain Diagnostic System Check? | -- | ||||||
Important: Before clearing the DTC, use the Scan Tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data. With the drive wheels rotating, does the Scan Tool Transmission ISS increase with the drive wheel speed? | -- | Go to Intermittent Conditions in Engine Controls | ||||||
3 |
Does the resistance measure within the specified range? | 1377-3355 Ω | ||||||
4 | Measure the resistance from terminal C3-7 to ground. Does the resistance measure greater than the specified value? | 50 K Ω | ||||||
Refer to General Electrical Diagnosis in Wiring Systems. Did you find and correct the condition? | -- | |||||||
6 |
Does the resistance measure within the specified range? | 1377-3355 Ω | ||||||
7 | Was the resistance measured in Step 3 greater than the specified value? | 3355 Ω | ||||||
8 |
Refer to General Electrical Diagnosis in Wiring Systems. Did you find and correct the condition? | -- | -- | |||||
9 |
Refer to General Electrical Diagnosis in Wiring Systems. Did you find and correct the condition? | -- | -- | |||||
10 | Test the high circuit (CKT 1230) and the low circuit (CKT 1231) of the ISS assembly for a short together. Refer to General Electrical Diagnosis in Wiring Systems. Did you find and correct the condition? | -- | -- | |||||
11 | Replace the ISS assembly. Refer to Vehicle Speed Sensor Replacement. Did you complete the replacement? | -- | -- | |||||
12 | Replace the VCM. Refer to VCM Replacement/Programming in Engine Controls. Did you complete the replacement? | -- | -- | |||||
13 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | -- | System OK |
