Troubleshooting code P1810 before disassembling left side of car to replace tfp position switch

MAUIGEORGE

MEMBER
2001 BUICK CENTURY
59,500 MILES

I have a code p1810 on my century. The car seems to be stuck in 3th gear, will not downshift and has no power going up hills or from a standing stop. I bought a new TFP position switch assy. P/n 24223197 thinking that I could access it from the oil pan on the bottom because I was told this switch is attached to the valve body? On this transmission the valve body is on the left side (of the car) and requires disassembly of the left wheel well and removal of the left side transmission cover to access it! Before I begin this process and tie up my garage for several hours (or maybe days?), Is there a way to test the switch to be sure it is defective? Could there may be some other defective part or system? Or is the TFP switch the most likely culprit? I do not want to tear it down, replace the switch, reassemble it and find out I still have the same problem! Being a A&P mechanic, I do not like to just replace parts not knowing weather or not they are bad? Thank you in advance for your advice? George

1 Reply

ASEMASTER6371

MECHANIC
52,797 POSTS

This is the description of the code and the needed checks. Codes never identify bad parts, just failed systems.

Roy

Circuit Description with 4T65-E Automatic Transaxle
The automatic transmission fluid pressure (TFP) manual valve position switch consists of six pressure switches (three normally-closed and three normally-open switches) Ignition voltage is applied to each of the switches. By grounding or opening one or more of these switches with fluid pressure from the manual valve the PCM can detect which gear range is selected.
If the PCM detects an invalid combination of inputs (LOW/HI/LOW or LOW/LOW/LOW) then DTC P1810 sets. If the PCM detects a gear range other than the one indicated then DTC P1810 sets. DTC P 1810 is a type B DTC.

Conditions for Running the DTC

� The engine speed is greater than 500 RPM for 5 seconds and not in fuel shut off.
� The system voltage is 9-18 volts.
Conditions for Setting the DTC
DTC P1810 sets when at least one of the following conditions occurs:

Condition 1
The TFP manual valve position switch indicates an invalid switch combination for 60 seconds.

Condition 2

� No VSS DTC P0502 or P0503.
� The vehicle speed is less than 5 km/h (3 mph).
� TFP manual valve position switch indicates REVERSE, D2 or D4 for 7 seconds at engine start up without indicating PARK or NEUTRAL.
Condition 3

� No TP sensor DTC P0121 P0122 or P0123.
� No VSS DTC P0502 or P0503.
� No At ISS sensor DTC P0716 or P017.
� No 1-2 3-4 SS valve DTC P0751 P0752 or P0753.
� No 2-3 SS valve DTC P0756 P0757 or P0758.
� The TP angle is greater than 9%.
� The vehicle speed is more than 8 km/h (5 mph).
� The engine torque is greater than 70 Nm (50 ft. Lbs.) And one of the following conditions occurs: The gear ratio indicates REVERSE, D4, D3 D2 or D1 and the TFP manual valve position switch indicates PARK or NEUTRAL for 5 seconds.
The gear ratio indicates D4 D3 D2 or D1 and the TFP manual valve position switch indicates REVERSE for 5 seconds.
The gear ratio indicates REVERSE and the TFP manual valve position switch indicates D4 D3 D2 or D1 for 5 seconds.

Action Taken When the DTC Sets

� The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met.
� The PCM commands maximum line pressure.
� The PCM freezes shift adapts.
� The PCM assumes D4 for shifting.
� The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Freeze Frame and Failure Records.
� The PCM stores DTC P1810 in PCM history during the second consecutive trip in which the Conditions for Setting the DTC are met.
Conditions for Clearing the MIL/DTC

� The PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
� A scan tool can clear the MIL/DTC.
� The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
� The PCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the PCM.
Test Description
The numbers below refer to the step numbers on the diagnostic table.

3. This step tests the indicated range signal to the manual valve range actually selected.
6. This step tests for correct voltage from the PCM to the transmission 20-way connector.
7. This step tests for a short together between signal circuit A and signal circuits B or C.