DTC P0842 or P0843
Diagnostic Instructions
DTC Descriptors
DTC P0842: Transmission Fluid Pressure
Switch 1 Circuit Low Voltage
DTC P0843: Transmission Fluid Pressure
Switch 1 Circuit High Voltage
Diagnostic Fault Information
Circuit
|
Short to Ground
|
Open/High Resistance
|
Short to Voltage
|
Signal Performance
|
TFP Switch 1 Signal
|
P0842
|
P0843
|
P0843
|
-
|
TFP Switch 3 Signal
|
P0872
|
P0873
|
P0873
|
-
|
TFP Switch 4 Signal
|
P0877
|
P0878
|
P0878
|
-
|
TFP Switch 5 Signal
|
P0989
|
P0990
|
P0990
|
--
|
Typical Scan Tool Data
Transmission Fluid Pressure
Switch 1
Circuit
|
Short to Ground
|
Open/High Resistance
|
Short to Voltage
|
Operating Conditions: Engine running,
normal operating temperature
Parameter Normal Range: High or
Low
|
Transmission Fluid Pressure Switch 1 Signal
|
Low
|
High
|
High
|
Circuit/System Description
The transmission fluid pressure (TFP) switch 1
assembly is part of the control solenoid valve assembly which has
no serviceable components. The transmission control
module (TCM) supplies a signal circuit to the TFP
switch 1. The TFP switch 1 has an internal case ground.
TFP switch 1 is normally closed or Low. When oil pressure is
present at the TFP switch 1, the switch is open or High. The
normally high clutch pressure control (PC) solenoid 2
controls pressure to the 3-5 reverse clutch regulator valve. The
TCM monitors the TFP switch 1 to determine the position of the
3-5 reverse clutch regulator valve. When the 3-5 reverse clutch is
commanded OFF, pressure is present on the TFP switch 1. When
the 3-5 reverse clutch is commanded ON, the 3-5 reverse clutch
regulator valve moves and pressure to the TFP switch 1 is
exhausted through the 3-5 reverse clutch regulator valve.
Conditions for Running the DTC
P0842 or P0843
• |
DTC P0711, P0712, P0713, P0716, P0717, P0722,
P0723, P0742, P0751, P0756, P0757, P0973, P0974, P0976, P0977,
P182E, or P1915 is not set. |
• |
The engine speed is 400 RPM or greater for
5 seconds. |
• |
The ignition voltage is 9.0 volts or
greater. |
• |
The transmission fluid temperature (TFT) is
-7 to +110°C (19-230°F). |
• |
The High Side Driver is ON. |
• |
The engine speed is 550 RPM or greater. |
Conditions for Setting the DTC
P0842
The TCM detects that the TFP switch 1 signal voltage
remains LOW after the 3-5-R clutch transitions from a HIGH pressure
state to a LOW pressure state. The TCM counts each incident. The
DTC sets when 42 counts are accumulated.
P0843
The TCM detects that the TFP switch 1 signal voltage
remains HIGH after the 3-5-R clutch transitions from a LOW pressure
state to a HIGH pressure state. The TCM counts each incident. The
DTC sets when 57 counts are accumulated.
Action Taken When the DTC Sets
• |
DTCs P0842 and P0843 are
Type C DTCs. |
• |
The TCM freezes transmission adaptive functions on
the 3-5-R clutch. |
Conditions for Clearing the DTC
DTCs P0842 and P0843 are Type C DTCs.
Diagnostic Aids
A TFP switch may malfunction due to normal debris in the
transmission fluid causing a TFP Switch DTC to intermittently set.
This type of condition should not be immediately noticeable to a
customer, as the switch outputs are used for shift adaptive
pressure and do not cause transmission symptoms unless the switch
malfunctions continuously for an extended period of time.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics
Connector End View Reference
Description and Operation
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Warning: Chock the wheels to
prevent the vehicle from moving. Failure to chock the wheels can
cause personal injury when the electrical system is
repaired.
- Engine ticking over in PARK with handbrake applied,
and drive wheels chocked.
- Monitor the Transmission Fluid Pressure Switch 1,
Transmission Fluid Pressure Switch 3, Transmission Fluid
Pressure Switch 4, and Transmission Fluid Pressure
Switch 5 parameters with a scan tool.
- Place the gear select lever in Park, Reverse, and
Neutral range. Verify the TFP switch parameter states are correct
for each range. Refer to
Transmission Fluid Pressure Switch Logic .
- Place the gear select lever in Drive range. Command
the shift transmission with a scan tool through all forward ranges.
Verify the TFP switch parameter states are correct for each range.
Refer to
Transmission Fluid Pressure Switch Logic .
⇒ |
If any TFP switch parameter state does not match
the logic table, replace the Q8 control solenoid valve
assembly. |
- After performing the above steps, verify that the DTC
does not reset by operating the vehicle within the Conditions for
Running the DTC. You may also operate the vehicle within the
conditions that you observed from the Freeze Frame/Failure Records
data. If the vehicle passes the Circuit/System Verification
procedure, refer to
Testing for Intermittent Conditions and Poor Connections .
Repair Instructions
Note:
Perform the
Diagnostic Repair Verification after completing the diagnostic
procedure.
Control Module References for control solenoid valve assembly
replacement, set-up, or programming
|