88 ford thunderbird turbo coupe automatic

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

Governor pressure controls the 1st and 2nd shifts. After that is the 3 and 4 solenoids. you would need to look at the pressure when driving(takes a scanner). pressure is 20 to 30 PSI from 1st to 2nd, depends on acceleration. After that the pressure will jump to 100+ psi. Did you replace the governor solenoid and sensor? They are on the passenger side of the transmission and sit in a block that detaches from the valve body.

What are you talking about auto shift control solenoid ? Which transmission does yours have ?
Automatic Transaxle - 3T40 Automatic Transaxle - 4T40-E
1-2 Shift Solenoid Valve
In transmission valve body
Transmission Component Location
Automatic Transmission Internal Connector End Views
2-3 Shift Solenoid Valve
In transmission valve body
Is there a DTC - diagnostic trouble code stored ? Which gear or gears are not working ?

Which transmission does yours have 4T65-E or 4T80-E ?

4T80-E
No Fourth Gear

Checks

Causes

1-2 Shift Solenoid Valve
?€¢
Inoperative
?€¢
Debris
?€¢
Pinched wires

3-4 Shift Valve Bore Plug

Misassembled

4th Band

Burned, slipping, missing

4th Servo Cover

Cracked

4th Servo Pin

Broken, seized

4th Servo Piston

Damaged

4th Servo Seals

Rolled, cut or damaged
4T65-E
Slipping or No Fourth Gear
Slipping or No Fourth Gear Checks
Cause

DEFINITION: A large engine RPM increase is noted in fourth gear, Drive range, with little or no vehicle forward speed increase. First, second, and third gear operation are normal. Shifts into fourth gear are soft or do not occur. Fourth gear ratio is 0.705:1.

Automatic Transmission Fluid Level
Low fluid level

Transmission Main Line Pressure
Low transmission main line pressure

Oil Filter Assembly
• The oil filter assembly (100) is missing, plugged, or damaged.
• The oil filter seal assembly (101) is missing or is damaged.

Control Valve Body Assembly
• The 3-4 shift valve (362) or the 4-3 manual downshift valve (360) is stuck or binding.
• Debris is found in the passages of the control valve body (301) or of the control valve body spacer plate and gasket assembly (396)

Case Cover Assembly
Distortion or damage occurs at the manual valve (404) or at the case cover (401), causing PRN oil leak.

Driven Sprocket Support Assembly
A plugged third clutch oil passage in the driven sprocket support assembly (609)

Fourth Clutch Assembly
• The clutch plates (500-502) are worn, damaged, or misassembled.
• A missing or not seated fourth clutch spring retaining ring (601)
• A damaged spring assembly (602) or piston (603)
• Worn or damaged fourth clutch piston seals (604, 605)

Third Clutch Sprag Assembly
• The sprag (720) was misassembled or backwards on the inner race (661).
• A damaged third clutch sprag assembly (653, 661, 719-721)

P0745 - Pressure Control Solenoid Malfunction Possible causes
- Low transmission fluid level
- Dirty transmission fluid
- Faulty line pressure solenoid valve
- Line pressure solenoid valve harness is open or shorted
- Line pressure solenoid valve circuit poor electrical connection Help with this
Tech notes
When the a transmission solenoid is malfunction, in most cases the problem is not the electrical part of the solenoid; the problem is foreign material obstructing the mechanical function of the solenoid or the flow of the fluid through the transmission valve body. If the transmission fluid is very dirty, it is recommend changing the transmission fluid and if possible removing the transmission pan for further diagnosis. Excessive debris or metal particles on the transmission pan could be an indication that there is a transmission mechanical failure and that the transmission will need to be rebuilt or replaced.
Help with this
When is the code detected?
The P0745 is detected when TCM detects an improper voltage drop when it tries to operate the solenoid valve.
Symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
- Transmission shift shock
P0745 Description
The line pressure solenoid valve regulates the oil pump discharge pressure to suit the driving condition in response to a signal sent from the Transmission Control Module (TCM).
TURBO BOOST PRESSURE SOLENOID VALVE DIESEL VAUXHALL MOVANO VIVARO RENAULT...

It might be as simple as a plugged filter. Worst case the transmission has gone out and needs rebuilt. Test it by starting off in 2 and see if the car will go to that gear and beyond or not.

time for a new one get one from a junk yard put it in or have someone do it for you

my tach and speedo work without moving plus it adds mileage to my odometer without moving at all why
1988 ford thunderbird turbo coupe

Ford is very common for tranny problems. Most likely your tranny will have to be rebuilt. As a mechanic myself, I would suggest taking to tranny specialist to see if i needs to be rebuilt, or if the electrical unit is faulty. It will have to be tested with voltmeter/ohmmeter/multi-tester

automatic transmission will not shift out of first gear. We have replace the solenoids in the valve body 3 of them , could the pcm computer be bad or does the tranny need to be rebuilt? The 2005 ford 250 has only 21000 miles but it did have a snow plow on it. It did pull trailers.