Fallas De Gmc Codigo Obdii Codigo P1860

DTC P0785: 3-2 SHIFT SOLENOID ELECTRICAL MALFUNCTION
NOTE: | Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK (PASSENGER CARS) prior to performing diagnostic procedures. For wire circuitidentification, see WIRING DIAGRAMS . |
Circuit Description
The 3-2 shift solenoid is a normally-closed 3-port on/off device which controls 3-2 downshift. Ignition voltage is supplied directly to solenoidthrough fused circuit. PCM commands solenoid on or off through ground circuit. During 3-2 downshift, 2-4 band applies as 3-4 clutch releases. PCM varies timing between 3-4 clutch release and 2-4 band applydepending on vehicle speed and throttle position. DTC P0785 is set if PCM detects a continuous open or short to ground in 3-2 shift solenoid circuit.
Conditions For Setting DTC P0785
DTC will setunder the following conditions:
* System voltage is 10-17 volts.
* Ignition is on.
* Engine is not in fuel cutoff mode.
* Engine speed is more than 450 RPM for 5 seconds.
* PCMcommands solenoid on and voltage remains high (battery voltage).
* PCM commands solenoid off and voltage remains low (zero voltage).
* All conditions are met for 5 seconds.
Action Taken ByPCM
PCM performs the following if DTC is set:
* Will illuminate MIL at first failure signal.
* Inhibits TCC engagement.
* Inhibits 4th gear if in hot mode.
* Freezes shift adaptsfrom being updated.
* Commands maximum line pressure.
* Commands a soft shift to 3rd gear.
* DTC P0785 will be stored in PCM history.
Diagnostic Procedure
NOTE: | If PCM replacementis necessary, ensure new PCM is reprogrammed. See COMPUTER RELEARN PROCEDURES article in APPLICATIONS & IDENTIFICATION. |
1. Connect scan tool to DLC. Turn ignition switch to ON position. Donot start engine. Using scan tool, record freeze frame and failure records for reference. Data will be lost when DTCs are cleared later in this test.
2. If DTCs P0740, P0753, P0758, P0785 and...