Transfer Case Range Malfunction - 4WD Low (4X4L)

DTC P1729, P1781 DETECTION CONDITION & POSSIBLE CAUSES

DTC P1729, P1781	4X4 LOW RANGE MALFUNCTION
DETECTION CONDITION	P1729 indicates 4WD shift control switch failure either open or shorted. P1781 indicates 4WD low position (closed) during KOEO self-test.
POSSIBLE CAUSE	Speedometer calibration. Damaged 4WD shift control switch. 4WD low harness open or shorted. Damaged electronic shift control module. Damaged PCM.
HINT	4WD Low Switch Description Provides an indication of when 4WD transfer case gear system is in low range. The PCM modifies the shift schedule for 4WD low transfer case gear ratio.
Courtesy of MAZDA MOTORS CORP.

DTC P1729, P1781 DIAGNOSTIC PROCEDURE

DTC P1729, P1781		4WD LOW RANGE MALFUNCTION
STEP	INSPECTION		ACTION
1	Was the PCM quick test performed?	Yes	Go to next step.
1	Was the PCM quick test performed?	No	Perform PCM quick test. See PCM QUICK TEST .
2	VERIFY 4WD LOW POSITION Verify vehicle is equipped with 4WD. Verify selector is in 2WD or 4WD high. Is the selection 2WD or 4WD high during PCM quick test?	Yes	Go to next step.
2		No	Select NEUTRAL position with shift lever. Select 2WD or 4WD high. Perform PCM quick test. See PCM QUICK TEST .
3	CHECK FOR INTERMITTENT CIRCUIT FAULT Key on, engine off (KOEO). Cycle the 4WD shift control switch to 4x2. Access 4WD low PID on WDS or equivalent tester and monitor while performing the following: Grasp the vehicle harness starting at the transfer case vehicle harness connector. Shake and bend a small section of the harness all the way to the PCM Tap the vehicle harness connector at the transfer case Shake and bend a small section of the harness between the instrument cluster connector and the PCM Does the 4WD low PID reading go ON/OFF during harness and connector movement?	Yes	Isolate fault and repair as necessary. Go to step 7.
3		No	Go to next step.
4	CHECK 4WD LOW SIGNAL FROM MODULE Key OFF. Disconnect PCM. Install breakout box, leave PCM disconnected. Key on, engine off (KOEO). Measure voltage between PCM test pin 68 (4WD low) and PCM test pin 24 (PWR GND) while cycling the 4WD shift control switch. Does voltage cycle?	Yes	Replace PCM. See POWERTRAIN CONTROL MODULE (PCM) REMOVAL / INSTALLATION . Go to step 7.
4		No	Go to next step.
5	CHECK RESISTANCE OF 4WD low WIRE Key OFF. Disconnect the 4WD module. Measure resistance between PCM test pin 68 (4WD low) and the four-wheel drive control module pin 1, circuit Y/LB at the four-wheel drive switch connector. Are the resistances less than 5.0 ohms?	Yes	Go to next step.
5		No	Repair open circuit. Go to step 7.
6	CHECK FOR SHORT TO POWER AND GROUND Connect 4WD module. Measure resistance between PCM test pin 68 (4WD low) circuit GY/B, and PCM test pin 24/103 (VPWR) circuit B/W. Measure resistance between PCM test pin 68 (4WD low) circuit GY/B, and PCM test pin 71/97 (VPWR) circuit R. Is each resistance greater than 10K ohms?	Yes	See TRANSFER CASE ELECTRONIC SHIFT ON - BOARD DIAGNOSIS for transfer case and 4WD system-diagnosis.
6		No	Repair short circuit. Go to next step.
7	VERIFY TROUBLESHOOTING OF DTCs COMPLETED Connect all disconnected connectors. Clear DTCs from PCM memory using WDS or equivalent tester. Perform PCM quick test. Is same DTC present?	Yes	Replace PCM. See POWERTRAIN CONTROL MODULE (PCM) REMOVAL / INSTALLATION . Repeat PCM quick test.
7		No	If any other DTC is present, Go to applicable DTC inspection. See DIAGNOSTIC TROUBLE CODE (DTC) INDEX - POWERTRAIN CONTROL MODULE (PCM) . If no DTC is present, troubleshooting is complete.