| Table 1: | Range Reference Table (For DTC P0730) |
| Table 2: | P1871 |
Range | Park/Neutral | Reverse | D | 3 | 2 | 1 | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Gear | N | R | 1st | 2nd | 3rd | 4th | 1st | 2nd | 3rd | 1st | 2nd | 3rd** | 1st | 2nd*** |
1-2 Shift Solenoid | ON | ON | ON | OFF | OFF | ON | ON | OFF | OFF | ON | OFF | OFF | ON | OFF |
2-3 Shift Solenoid | OFF | OFF | OFF | OFF | ON | ON | OFF | OFF | ON | OFF | OFF | ON | OFF | OFF |
2nd Clutch | -- | -- | -- | A | A* | A* | -- | A | A* | -- | A | A* | -- | A |
2nd Roller Clutch | -- | -- | -- | H | O | -- | -- | H | O | -- | H | O | -- | H |
Int./4th Band | -- | -- | -- | -- | -- | A | -- | -- | -- | -- | A | -- | -- | A |
Reverse Clutch | -- | A | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
Coast Clutch | -- | -- | -- | -- | -- | -- | A | A | A | A | A | A | A | A |
Input Sprag | -- | -- | H | H | H | O | H | H | H | H | H | H | H | H |
Direct Clutch | -- | -- | -- | -- | A | A | -- | -- | A | -- | -- | A | -- | -- |
Forward Clutch | -- | -- | A | A | A | A* | A | A | A | A | A | A | A | A |
Lo/Rev Band | A | A | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | A | -- |
Lo Roller Clutch | -- | -- | H | O | O | O | H | O | O | H | O | O | H | O |
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Circuit Description
The Powertrain Control Module (PCM) calculates gear ratio based on the transmission input and output speeds. The PCM compares the known transmission gear ratio to the calculated ratio for the selected gear range.
When the PCM detects an unknown transmission gear ratio, then DTC P1871 sets. DTC P1871 is a type D DTC.
Conditions for Setting the DTC
| • | No VSS DTC P0502 |
| • | No TFT DTCs P0712 or P0713 |
| • | No TFP Val. Position Sw. DTC P1810 |
| • | No Input Speed Sensor DTCs P0716 or P0717 |
| • | No TP Sensor DTCs P0121, P0122, or P0123 |
| • | The engine is running. |
| • | The TFP Val. Position Sw. is not indicating Park or Neutral. |
| • | The TP is greater than 15%. |
| • | The vehicle speed is greater than 16 km/h (10 mph). |
| • | The transmission fluid temperature is greater than 0°C (32°F). |
| • | The MAP is 40-105 kPa. |
| • | The engine speed is less then 6500 RPM. |
| • | The last manual range change was at least 3 seconds ago. |
And one of the following conditions occurs:
| • | The gear ratio is less than 1:2.87, or greater than 1:3.13, for 7 seconds. |
| • | The gear ratio is less than 1:1.54, or greater than 1:1.71, for 7 seconds. |
| • | The gear ratio is less than 1:0.97, or greater than 1:1.07, for 7 seconds. |
| • | The gear ratio is less than 1:0.61, or greater than 1:0.72, for 7 seconds. |
| • | The gear ratio is less than 1:2.02, or greater than 1:2.23, for 7 seconds. |
Action Taken When the DTC Sets
| • | The PCM commands maximum line pressure. |
| • | The PCM freezes shift adapts from being updated. |
| • | The PCM does not illuminate the Malfunction Indicator Lamp (MIL). |
| • | DTC P1871 is stored in the PCM history. |
Conditions for Clearing the DTC
| • | A scan tool can clear the DTC from the PCM history. The PCM clears the DTC from the PCM history if the vehicle completes 40 warm-up cycles without a failure reported. |
| • | The PCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the PCM. |
Diagnostic Aids
| • | Inspect for intermittent Automatic Transmission Input (Shaft) Speed Sensor (A/T ISS) circuit problems. |
| • | Inspect for intermittent Automatic Transmission Output (Shaft) Speed Sensor (A/T OSS) circuit problems. |
| • | Inspect for an incorrect calibration. |
Test Description
The numbers below refer to the Step numbers on the diagnostic table.
-
This Step tests for low fluid level, which may cause slipping, and result in an undefined gear ratio.
-
This Step verifies that the correct gear ratios occur for commanded gears.
-
This Step tests for low line pressure.
-
When DTC P1871 sets, the PCM commands maximum line pressure and does not inhibit TCC engagement. This can lead to excessive heat build-up, causing the Torque Converter to "balloon." You must replace the Torque Converter.
Step | Action | Value(s) | Yes | No | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to | |||||||||||||
2 | Visually inspect the transmission cooling system for fluid leaks. Refer to Fluid Leak Diagnosis and Repair . Did you find and correct the condition? | -- | ||||||||||||||
Have you performed the transmission fluid checking procedure? | -- | Go to Transmission Fluid Check | ||||||||||||||
Important: Before clearing the DTCs, use the scan tool in order to record the Failure Records for reference. The Clear Info function will erase the data. Did the commanded gear ratio match the specified ranges? | Reverse: 1:2.02-1:2.23 1st: 1:2.87-1:3.13 2nd: 1:1.54-1:1.71 3rd: 1:0.93-1:1.05 4th: 1:0.61-1:0.72 | Go to Diagnostic Aids | ||||||||||||||
Perform the line pressure check. Refer to Line Pressure Check Procedure . Did you find and correct the condition? | -- | |||||||||||||||
6 | Inspect for clutch slippage. Refer to Symptom Diagnosis table, No Torque Converter Clutch Apply/TCC Slipping/Soft TCC Apply . Did you find and correct the condition? | -- | -- | |||||||||||||
Replace the torque converter. Refer to Test Description 7 . Is the replacement complete? | -- | -- | ||||||||||||||
8 | In order to verify your repair, perform the following procedure:
Has the test run and passed? | -- | System OK |
