Need location of HIGH Gear Pressure Switch on gm transmission

DTC P0877: Transmission Fluid Pressure (TFP) Switch 4 Circuit Low Voltage

The transmission fluid pressure (TFP) switch 4 is part of the control solenoid (w/body and TCM) valve assembly and is not serviced separately. The TCM supplies 12 volts to the TFP switch 4 on the TFP switch 4 signal circuit; the TFP switch 4 has an internal case ground. TFP switch 4 is normally closed, Low. When oil pressure is present at the TFP switch 4, the switch is open, high. The normally low clutch pressure control (PC) solenoid 4-5 controls the transmission fluid to the 1-2-3-4 clutch. The TCM monitors the normally closed TFP switch 4 signal circuit to determine the 1-2-3-4 clutch status.
P0877
The TCM detects that the TFP switch 4 signal voltage remains low, 0 volts when the 1-2-3-4 clutch is commanded ON for 5.5 seconds or greater.

Action Taken When the DTC Sets
• DTCs P0877 and P0878 are Type C DTCs.
• The TCM freezes transmission adaptive functions.

Circuit/System Testing
Ensure the TFT is near the temperature displayed in the Failure Records.
Start the engine and place the transmission range selector in D6.
Observe the TFP switch 4 parameter while commanding 4th gear and then commanding 5th gear with the scan tool. The TFP Switch 4 should transition from High in 4th gear to Low in 5th gear.
? If the TFP switch 4 parameter state does not change, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .
? If no concerns are found, replace the control solenoid (w/body and TCM) valve assembly.
Component Testing
Perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection .
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control solenoid (w/body and TCM) valve assembly replacement - refer to Control Module References for replacement, setup, and programming.
Perform the Service Fast Learn Adapts

The high pressure runs in the smaller diameter tube.

Most computer controlled transmissions have what is called a pressure control solenoid. IF there is a problem in the transmission the computer may try to compensate by increasing pressure.

Also when a PC solenoid is bad it defaults to high pressure.

The 3rd gear neutralize is probably the reason for the high pressure. The longer you let it go the more damage that will be done to the transmission. If the vehicle is worth it, pay to get it fixed. It is a lot cheaper than buying a newer vehicle, and when you have your own car you know what it is.

Hope this helps.

DTC P0736 - Reverse incorrect gear ratio

The clutch pressure control (PC) solenoid 2 flows fluid to the 3-5-R clutch when commanded OFF and exhausts fluid when commanded ON. The clutch PC solenoid 2 regulates the transmission fluid pressure to the 3-5-R clutch. The transmission fluid pressure (TFP) switch 1 Opens (High) under fluid pressure and closes (Low) when no pressure is present. The transmission control module (TCM) calculates gear ratio based on data from the automatic transmission input speed sensor (ISS) and the output speed sensor (OSS). The TCM compares the known transmission gear ratio to a calculated gear ratio for each commanded gear.

Circuit/System Verification:
Operate the vehicle to induce a shift from second to third gear while observing TFP Switch 1. Perform this action 2 times. The TFP Switch 1 should change states from Low to High. If the TFP Switch does not change states and no other DTCs set, replace the control solenoid (w/body and TCM) valve assembly. If any other DTCs set, diagnose that DTC first.
Operate the vehicle to obtain sixth gear 2 times and then check for DTCs other than DTC P0736.If any other DTCs set, diagnose that DTC first. If no other DTC sets, continue on with diagnostics.
Operate the vehicle by shifting from Park to Reverse, then while in reverse, operate the vehicle with the calculated throttle position greater than 8% for 5 seconds, perform this maneuver a minimum of 3 times. If the DTC P0736 resets, go to Component Testing.

Component Testing:
Perform the line test procedure.
Inspect the check ball 5 for possible sticking or damage. If you found a concern with this check ball, repair the concern.
Inspect the shift select valve 3 for sticking or damage. If you found a concern with the shift select valve 3, repair or replace the valve or valve body.
Inspect the R-1 (Low and Reverse clutch) assembly for wear or damage. If you found a R-1 assembly concern, repair or replace the R-1 assembly as necessary.

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DTC P0736 - Reverse incorrect gear ratio

The clutch pressure control (PC) solenoid 2 flows fluid to the 3-5-R clutch when commanded OFF and exhausts fluid when commanded ON. The clutch PC solenoid 2 regulates the transmission fluid pressure to the 3-5-R clutch. The transmission fluid pressure (TFP) switch 1 Opens (High) under fluid pressure and closes (Low) when no pressure is present. The transmission control module (TCM) calculates gear ratio based on data from the automatic transmission input speed sensor (ISS) and the output speed sensor (OSS). The TCM compares the known transmission gear ratio to a calculated gear ratio for each commanded gear.

Circuit/System Verification:
Operate the vehicle to induce a shift from second to third gear while observing TFP Switch 1. Perform this action 2 times. The TFP Switch 1 should change states from Low to High. If the TFP Switch does not change states and no other DTCs set, replace the control solenoid (w/body and TCM) valve assembly. If any other DTCs set, diagnose that DTC first.
Operate the vehicle to obtain sixth gear 2 times and then check for DTCs other than DTC P0736.If any other DTCs set, diagnose that DTC first. If no other DTC sets, continue on with diagnostics.
Operate the vehicle by shifting from Park to Reverse, then while in reverse, operate the vehicle with the calculated throttle position greater than 8% for 5 seconds, perform this maneuver a minimum of 3 times. If the DTC P0736 resets, go to Component Testing.

Component Testing:
Perform the line test procedure.
Inspect the check ball 5 for possible sticking or damage. If you found a concern with this check ball, repair the concern.
Inspect the shift select valve 3 for sticking or damage. If you found a concern with the shift select valve 3, repair or replace the valve or valve body.
Inspect the R-1 (Low and Reverse clutch) assembly for wear or damage. If you found a R-1 assembly concern, repair or replace the R-1 assembly as necessary.

Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day and Happy New Year.

Hi Greg:
DTC P0736 - Reverse incorrect gear ratio

The clutch pressure control (PC) solenoid 2 flows fluid to the 3-5-R clutch when commanded OFF and exhausts fluid when commanded ON. The clutch PC solenoid 2 regulates the transmission fluid pressure to the 3-5-R clutch. The transmission fluid pressure (TFP) switch 1 Opens (High) under fluid pressure and closes (Low) when no pressure is present. The transmission control module (TCM) calculates gear ratio based on data from the automatic transmission input speed sensor (ISS) and the output speed sensor (OSS). The TCM compares the known transmission gear ratio to a calculated gear ratio for each commanded gear.

Circuit/System Verification:
Operate the vehicle to induce a shift from second to third gear while observing TFP Switch 1. Perform this action 2 times. The TFP Switch 1 should change states from Low to High. If the TFP Switch does not change states and no other DTCs set, replace the control solenoid (w/body and TCM) valve assembly. If any other DTCs set, diagnose that DTC first.
Operate the vehicle to obtain sixth gear 2 times and then check for DTCs other than DTC P0736.If any other DTCs set, diagnose that DTC first. If no other DTC sets, continue on with diagnostics.
Operate the vehicle by shifting from Park to Reverse, then while in reverse, operate the vehicle with the calculated throttle position greater than 8% for 5 seconds, perform this maneuver a minimum of 3 times. If the DTC P0736 resets, go to Component Testing.

Component Testing:
Perform the line test procedure.
Inspect the check ball 5 for possible sticking or damage. If you found a concern with this check ball, repair the concern.
Inspect the shift select valve 3 for sticking or damage. If you found a concern with the shift select valve 3, repair or replace the valve or valve body.
Inspect the R-1 (Low and Reverse clutch) assembly for wear or damage. If you found a R-1 assembly concern, repair or replace the R-1 assembly as necessary.

Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

700=TRANSMISSION CONTROL SYSTEM, NEED TO READ TRANSMISSION DTC's ON THE DRBIII(R)
732= TRANSMISSION.....POSSIBLE CAUSES----RELATED DTC'S PRESENT, TRANSMISSION SOLENOID/PRESSURE SWITCH ASSEMBLY, INTERNAL TRANSMISSION, INTERMITTENT GEAR RATIO ERRORS..
Hope this helps ??

Not vacumm controlled anymore.Hard shifts are caused by high line pressure. you may have a trouble code stored in the computer and transmissions code back then did not always turn the check engine light on.A stored code will trigger high line pressure.You could have a bad force motor and this was common for 93 and 94, infact gm changed the solenoid and you will need to buy the late design if needed.I would start by having a shop pull the codes.

be 1988 and Im sure it has high miles, sound like worn transmission, transmission flush and replace it with new fluid might help some. get use tranny from a junk yard better and cost lot less than rebuilt. being GM mechanic for many years i see transmission on a truck with 100k tend to have leaks or need rebuilding. again i see some have better luck but rear.

P1757 1T CCM 1996-2003 Cherokee, Grand Cherokee A/T Governor Pressure Above 3 PSI In Gear At 0 MPH Conditions: Engine started; vehicle driven to a speed over 30 mph, and the PCM detected the Governor Pressure Sensor was more than 3 psi with the requested pressure at 0 psi (95% duty cycle command) for 2.65 seconds. The fault must occur twice on one trip to set the code. Possible Causes: Check for the presence of other A/T related trouble codes Governor pressure Sensor is damaged or has failed Governor pressure Sensor VREF (5v) circuit is open or shorted Transmission valve body is leaking, damaged or has failed PCM has failed P1762 1T CCM 1996-2003 Cherokee, Grand Cherokee A/T Governor Pressure Sensor Offset Volts Too High/Low Conditions: Key on or engine running. Gear selector in Park or Neutral. PCM detected an out-of-range Governor Pressure Sensor signal for 1.3 seconds. The fault must occur 3 times on one trip to set a code. Possible Causes: Governor pressure Sensor VREF (5v) circuit is open Governor pressure Sensor ground circuit is open P/N switch is damaged or has failed (not operating properly) Transmission fluid has excessive debris or it is contaminated PCM has failed