P0841-LR PRESSURE SWITCH RATIONALITY

For a complete wiring diagram Refer to Section 8W.

Theory of Operation

The Transmission system uses three pressure switches to monitor the fluid pressure in the LR, 2/4, and OD elements. The pressure switches are continuously monitored for the correct states in each gear. If a set condition is identified, 1st gear and torque converter lock-up (EMCC) will be inhibited. The vehicle will launch in 2nd gear and shift normally through the gears without allowing EMCC. If during the same key start, the set condition is no longer valid, the transmission will return to normal operation (1st and EMCC available). Limp-in will not occur unless DTC P0841 is accompanied by a code P0706 and the MIL will illuminate after 5 minutes of substituted operation.

When Monitored:
Whenever the engine is running.
Set Condition:
The DTC is set if one of the pressure switches are open or closed at the wrong time in a given gear. If the problem is identified for 3 successive key starts, the transmission will go into limp-in mode and the MIL will turn on after 10 seconds of vehicle operation.

Possible Causes

LOSS OF PRIME DTC PRESENT

(T50) L/R PRESSURE SWITCH SENSE CIRCUIT OPEN

(T50) L/R PRESSURE SWITCH SENSE CIRCUIT SHORT TO GROUND

(T50) L/R PRESSURE SWITCH SENSE CIRCUIT SHORT TO VOLTAGE

TRANSMISSION SOLENOID/PRESSURE SWITCH ASSEMBLY

POWERTRAIN CONTROL MODULE

Always perform the 42RLE Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)

PRESSURE SWITCH STATES

GEAR	L/R	2/4	OD
R	OPEN	OPEN	OPEN
P/N	CLOSED	OPEN	OPEN
1st	CLOSED	OPEN	OPEN
2nd	OPEN	CLOSED	OPEN
D	OPEN	OPEN	CLOSED
OD	OPEN	CLOSED	CLOSED

Diagnostic Test

1. DETERMINING IF RELATED TIPM TCM POWER CONTROL CIRCUIT DTCS PRESENT

With the scan tool, read TIPM DTCs.

Are there any TIPM TCM Power Control Circuit DTCs present also?

Yes

Refer to the Transmission category and perform the appropriate symptom.

Go To 2

2. CHECK FOR LOSS OF PRIME DTC

With the scan tool, check for other Transmission DTCs.

Is the DTC P0944 present also?

Yes

Refer to the Transmission category and perform the appropriate symptom.

Go To 3

3. CHECK TO SEE IF P0841 IS CURRENT

With the scan tool, view DTCs.

Is the status active for this DTC or is the STARTS SINCE SET counter 2 or less?

Yes

Go To 4

Go To 8

4. PCM AND WIRING

Turn the ignition off to the lock position.
Remove the Ignition Switch Feed fuse from the TIPM.

CAUTION: Removal of the Ignition Switch Feed fuse from the TIPM will prevent the vehicle from being started in gear.

WARNING: The Ignition Switch Feed fuse must be removed from the TIPM. Failure to do so can result in personal injury or death.

Install the Transmission Simulator, Miller tool #8333 and the Electronic Transmission Adapter kit.
Ignition on, engine not running.
With the Transmission Simulator, turn the Pressure Switch selector to L/R.
With the scan tool, monitor the L/R Pressure Switch state while pressing the Pressure Switch Test button on the Transmission Simulator.

Did the L/R Pressure Switch state change?

Yes

Replace the Transmission Solenoid/Pressure Switch Assembly per the Service Information.

Perform 42RLE TRANSMISSION VERIFICATION TEST (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)

Go To 5

5. (T50) L/R PRESSURE SWITCH SENSE CIRCUIT OPEN

Turn the ignition off to the lock position.
Disconnect the PCM C4 harness connector.
Disconnect the Transmission Solenoid/Pressure Switch Assembly harness connector.

CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller tool #8815 to perform diagnosis.

Measure the resistance of the (T50) L/R Pressure Switch Sense circuit between the Transmission Solenoid/Pressure Switch Assembly harness connector and the appropriate terminal of Miller tool #8815.

Is the resistance above 5.0 ohms?

Yes

Repair the (T50) L/R Pressure Switch Sense circuit for an open.

Perform 42RLE TRANSMISSION VERIFICATION TEST (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)

Go To 6

6. (T50) L/R PRESSURE SWITCH SENSE CIRCUIT SHORT TO GROUND

Measure the resistance between ground and the (T50) L/R Pressure Switch Sense circuit.

Is the resistance below 5.0 ohms?

Yes

Repair the (T50) L/R Pressure Switch Sense circuit for a short to ground.

Perform 42RLE TRANSMISSION VERIFICATION TEST (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)

Go To 7

7. (T50) L/R PRESSURE SWITCH SENSE CIRCUIT SHORT TO VOLTAGE

Ignition on, engine not running.
With the scan tool under TIPM, actuate the Transmission.
Measure the voltage of the (T50) L/R Pressure Switch Sense circuit.

Is the voltage above 0.5 volts?

Yes

Repair the (T50) L/R Pressure Switch Sense circuit for a short to voltage.

Perform 42RLE TRANSMISSION VERIFICATION TEST (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)

Using the schematics as a guide, check the Powertrain Control Module (PCM) terminals for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace and program the PCM per the Service Information. With the scan tool, perform QUICK LEARN.
Perform 42RLE TRANSMISSION VERIFICATION TEST (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)

8. INTERMITTENT WIRING AND CONNECTORS

The conditions necessary to set the DTC are not present at this time.
Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.
Wiggle the wires while checking for shorted and open circuits.
With the scan tool, check the DTC EVENT DATA to help identify the conditions in which the DTC was set.

Were there any problems found?

Yes

Repair as necessary.

Perform 42RLE TRANSMISSION VERIFICATION TEST (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 42RLE - STANDARD PROCEDURE)

Test Complete.