DTC P0842
Circuit Description
The pressure switch manifold (PSM) is a multiple-switch assembly made up of three normally open (N/O) and one normally closed (N/C) pressure switches. The C pressure switch monitors C shift valve positioning and relays it to the transmission control module (TCM). When the C pressure switch is in the open state, C shift valve should be in the unstroked position.
DTC P0842 is a type A DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0842 Pressure Switch C Circuit Low/Stuck Closed
Conditions for Running the DTC
•The components are powered and ignition voltage is greater than 9.0 volts and less than 18 volts.
•Engine speed is greater than 200 RPM and less than 7,500 RPM for 5 seconds.
•C shift valve is commanded to the OFF, unstroked, position.
Conditions for Setting the DTC
DTC P0842 sets when C solenoid is commanded OFF and pressure switch C status remains ON for 2–6 seconds, depending on fluid temperature.
Action Taken When the DTC Sets
•The TCM illuminates the malfunction indicator lamp (MIL)
•When in a forward range and shifting is completed, the transmission will fail to another forward range, unless the transmission is compromised by over speeding or direction change, then the transmission will shift to NEUTRAL.
•When in a forward range and the shift is in process, the transmission will return to a previous range, except for 1–2 shifts and 2–1 shifts which will be completed.
•When in NEUTRAL or REVERSE, the transmission will fail to NEUTRAL.
•While diagnostic response is active, the shift selector is moved from a forward range to NEUTRAL or from a forward range to REVERSE, then the transmission will shift to NEUTRAL.
•DTC P0842 will be stored in TCM history.
•The TCM freezes shift adapts.
•The TCM inhibits torque converter clutch (TCC) engagement.
Conditions for Clearing the DTC
A scan tool can clear the code from TCM history. The TCM automatically clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without failure.
Diagnostic Aids
•Inspect the wiring for poor electrical connections at the TCM. Inspect for the following conditions:
◦A bent terminal
◦A backed-out terminal
◦A damaged terminal
◦Poor terminal tension
◦A chafed wire
◦A broken wire inside the insulation
•When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.
•You may have to drive the vehicle in order to experience a condition.
•This DTC may indicate that C solenoid is mechanically defective or the shift valve is stuck in the stroked state.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
5.This step tests the TCM response function.
6.This step tests the transmission wiring harness integrity.
7.This step tests and evaluates the internal wiring harness.
8.This step tests the PSM for a failed condition.
Step
Action
Value
Yes
No
Schematic Reference:Automatic Transmission Controls Schematics
1
Did you perform the Diagnostic System Check – Vehicle?
Go to Step 2
Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2
Measure the transmission fluid level. Refer to Transmission Fluid Level and Condition Check.
Is the transmission fluid level correct?
Go to Step 3
Go to Transmission Fluid Level and Condition Check
3
Measure line pressure. Refer to Line Pressure Check.
Is the pressure within the specified value?
Go to Step 4
Go to Symptoms - Automatic Transmission
4
•Install the scan tool.
•Turn ON the ignition, with the engine OFF.
Important: Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data.
•Record the DTC Freeze Frame and Failure Records.
•Clear the DTC.
•Start the engine.
•Using the scan tool, monitor TFP SW. C status.
Does the scan tool indicate TFP SW. C status is ON?
Go to Diagnostic Aids
Go to Step 5
5
•Turn the ignition OFF.
•Disconnect C2 connector (RED) at the TCM.
•Install the J 39700 breakout box and the J 43799 breakout box adapter at C2 connector.
•Connect terminal 1 to a known good ground.
•Turn ON the ignition, with the engine OFF.
Does the scan tool indicate TFP SW. C status is ON when grounded and OFF when open?
Go to Step 6
Go to Step 15
6
•Turn the ignition OFF.
•Connect the C2 connector (RED) to the TCM.
•Disconnect the transmission 20-way connector.
•Turn the ignition ON. Additional DTCs might be set.
•Connect terminal D to a known good ground.
Does the scan tool indicate TFP SW. C status is ON when grounded and OFF when open?
Go to Step 7
Go to Step 14
7
•Remove the oil pan. Refer to Oil Pan Replacement.
•Disconnect the AT internal wiring harness from the PSM and ground terminal A.
Does the scan tool indicate TFP SW. C status is ON when grounded and OFF when open?
Go to Step 8
Go to Step 13
8
•Remove the PSM from the control valve body and leave the internal harness connected. Refer to Pressure Switch Manifold Replacement.
•Provide a ground connection for the PSM to either the control valve body or the transmission main case.
•Using the eraser end of a pencil, push gently on the pressure switch C membrane.
Does the scan tool indicate TFP SW. C status is ON when grounded and OFF when open?
Go to Step 9
Go to Step 12
9
Remove the control valve body and inspect for a stuck or sticking C shift valve. Refer to Control Valve Body Disassemble.
Was the C shift valve stuck or sticking?
Go to Step 11
Go to Step 10
10
Replace the C shift solenoid and install the control valve body. Refer to Control Valve Body Replacement.
Did you replace the solenoid and install the control valve body?
Go to Step 16
11
Replace the control valve body assembly. Refer to Control Valve Body Replacement.
Did you complete the replacement?
Go to Step 16
12
Replace the PSM. Refer to Pressure Switch Manifold Replacement.
Did you complete the replacement?
Go to Step 16
13
Replace the AT internal wiring harness. Refer to Wiring Harness Replacement.
Did you complete the replacement?
Go to Step 16
14
Repair the engine wiring harness circuit for an open or short. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you complete the repair?
Go to Step 16
15
Important: In most cases, the TCM is not at fault. Investigate thoroughly before replacing the TCM.
Replace the TCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and progr
amming.
Did you complete the replacement?
Go to Step 16
16
Perform the following procedure in order to verify the repair:
•Clear the DTC.
•Start the engine.
•Use the scan tool, monitor TFP SW. C status.
•Select Specific DTC.
•Enter DTC P0842.
Has the test run and passed?
