Transmission Range Switch Circuit Diagnosis. GMC Truck GMC K Sierra

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 1999 🢒 GMC K Sierra - 4WD 🢒 Engine 🢒 Engine Controls - 4.8L, 5.3L, and 6.0L 🢒 Transmission Range Switch Circuit Diagnosis

Table 1:	Transmission Range Switch Valid Input Combinations
Table 2:	Transaxle Range Switch Circuit

Engine Controls Component Views
Cell 21: Instrument Cluster, Automatic Transmission
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The transmission on this vehicle has a Park Neutral Position (PNP) and Back-up switch. This switch incorporates a transmission range selector switch. There are four inputs (PRND A, B, C, P) which are switches to ground. The four switches have an unique switch pattern. The PCM uses the combination of the switch patterns in order to determine the gear selected by the driver.

Diagnostic Aids

Important: Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.

The following may cause an intermittent:

•	Inspect for poor connections. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.

•

Corrosion

•	Mis-routed harness

•	Rubbed through wire insulation

•	Broken wire inside the insulation

•	Manipulate related wiring and connectors while observing the PRND Range parameters (PRND A, B, C, P) on the scan tool. If the manipulation causes an intermittent, the corresponding parameter changes on the scan tool.

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The table below is the normal state that each gear range should indicate. ON indicates the circuit is low (switched/shorted to a ground). OFF indicates the circuit is high (open). Another parameter to display is PRND Range. This parameter displays the current gear range the transmission is in. When there is an invalid gear range, the parameter indicates Invalid.

Transmission Range Switch Valid Input Combinations

Gear Selector Position	Scan Tool Trans Range ABCP Display
Gear Selector Position	A	B	C	P
Park (P)	ON	OFF	OFF	ON
Reverse (R)	ON	ON	OFF	OFF
Neutral (N)	OFF	ON	OFF	ON
Drive4 (OD)	OFF	ON	ON	OFF
Drive3 (3)	ON	ON	ON	ON
Drive2 (2)	ON	OFF	ON	OFF
Drive 1 (1)	OFF	OFF	ON	ON

Test Description

The numbers below refer to the step numbers on the diagnostic table.

This verifies whether a malfunction is present. If the PCM does not detect any invalid ranges, this indicates the fault is not present. You may have repaired the fault when the switch was adjusted.

Any circuit that you suspect is causing an intermittent condition, thoroughly inspect for the following:

•	Backed out terminals

•	Improper mating

•	Broken locks

•	Improperly formed or damaged terminals

•	Poor terminal to wiring connections

•	Physical damage to the wiring harness

A circuit malfunction causes the Trans Range to display an invalid range on the scan tool. Jumping each circuit to ground simulates the trans range switch operation and tests the circuitry and PCM. While the transmission range switch is disconnected and the circuits are not grounded, the scan tool should indicate OFF. A value that indicates ON with no jumper to ground indicates a grounded circuit or malfunctioning PCM.

Transaxle Range Switch Circuit

Step	Action	Value(s)	Yes	No
1	Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?	--	Go to Step 2	Go to Powertrain On Board Diagnostic (OBD) System Check
2	Important: Adjust the PNP switch and the shift cable/lever before proceeding with this diagnostic table. Refer to Park/Neutral Position Switch Adjustment (4L60E) or Park/Neutral Position Switch Adjustment (4L80E) in Transmission. Turn ON the ignition leaving the engine OFF. Install a scan tool. Move the gear selector through all the gear ranges while monitoring the PRND A, B, C, P and the Trans PRND parameter on the scan tool. Does the scan tool indicate an invalid position in any of the gear ranges?	--	Go to Step 3	Go to Diagnostic Aids
3	Compare the scan tool values with the Transmission Range Switch Valid Input Combinations table. Does the scan tool display all the circuits as OFF?	--	Go to Step 4	Go to Step 5
4	Test the PNP switch ground circuit for an open or poor connection. If you find a condition, repair as necessary. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition?	--	System OK	Go to Step 5
5	Move the gear selector through all of the gear ranges and observe which circuits do not correspond with the Transmission Range Switch Valid Input Combinations table. Disconnect the trans range switch electrical connector. Jumper the circuit with the incorrect value to ground. Does the scan tool change from OFF to ON when the circuit was jumped to ground?	--	Go to Step 8	Go to Step 6
6	Test the affected circuit for an open or a short to ground and repair as necessary. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition?	--	System OK	Go to Step 7
7	Inspect for a poor connection at the PCM connector and repair as necessary. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems. If you find a poor connection repair the condition as necessary. Refer to Repairing Connector Terminals in Wiring Systems. Did you find and correct the condition?	--	System OK	Go to Step 10
8	Inspect for a poor connection at the PNP/Back Up Switch electrical connector. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems. If you find a poor connection repair the condition as necessary. Refer to Repairing Connector Terminals in Wiring Systems. Did you find and correct the condition?	--	System OK	Go to Step 9
9	Replace the PNP/Back Up Switch. Refer to Park/Neutral Position Switch Replacement (4L60E) or Park/Neutral Position Switch Replacement (4L80E) in Transmission. Is the action complete?	--	System OK	--
10	Important:: Program the replacement PCM. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is the action complete?	--	System OK	--