| Table 1: | TFP Manual Valve Position Switch Logic |
| Table 2: | DTC P1810 TFP Manual Valve Position Switch Circuit Malfunction |
Circuit Description
The automatic transmission fluid pressure (TFP) manual valve position switch consists of five pressure switches (two normally-closed and three normally-open), and a transmission fluid temperature (TFT) sensor combined into one unit. The combined unit mounts on the valve body. The vehicle control module (VCM) supplies the battery voltage for each range signal. By grounding one or more of these circuits through various combinations of the pressure switches, the VCM detects which manual valve position you select. The VCM compares the actual voltage combination of the switches to a TFP manual valve position switch combination chart stored in memory.
The TFP manual valve position switch cannot distinguish between PARK and NEUTRAL because the monitored valve body pressures are identical. With the engine OFF and the ignition switch in the RUN position, the TFP manual valve position switch indicates PARK/NEUTRAL. Disconnecting the transmission 20-way connector removes the ground potential for the three range signals to the VCM. In this case, with the engine OFF, and the ignition switch in the RUN position, D2 will be indicated.
When the VCM detects an invalid state of the TFP manual valve position switch or the TFP manual valve position switch circuit by deciphering the TFP manual valve position switch inputs, then DTC P1810 sets. DTC P1810 is a type B DTC.
Conditions for Running the DTC
| • | No VSS assembly DTCs P0502 or P0503. |
| • | The system voltage is 10-19 volts. |
| • | The engine speed is greater than 450 RPM for 5 seconds. |
| • | The engine is not in fuel cutoff. |
| • | The engine torque is 40-400 lb ft. |
| • | The engine vacuum is 0-105 kPa. |
Conditions for Setting the DTC
DTC P1810 sets if any of the following conditions occurs:
Condition 1
The VCM detects an illegal TFP manual valve position switch state for 60 seconds.
Condition 2
| • | The engine speed is less than 80 RPM for 0.1 second; |
| then the engine speed is 80-550 RPM for 0.1 second; |
| then the engine speed is greater than 550 RPM. |
| • | The vehicle speed is less than 3 km/h (2 mph). |
| • | The VCM detects a gear range of D2, D4 or REVERSE during an engine start. |
| • | All conditions met for 5 seconds. |
Condition 3
| • | The TP angle is 10-50%. |
| • | The VCM commands fourth gear. |
| • | The TCC is locked ON for 10 seconds. |
| • | The speed ratio is 0.6-0.75 (speed ratio is engine speed divided by transmission output speed). |
| • | The VCM detects a gear range of PARK or NEUTRAL when the vehicle is operating in D4. |
| • | All conditions met for 10 seconds. |
Action Taken When the DTC Sets
| • | The VCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the conditions for setting the DTC are met. |
| • | The VCM commands D2 line pressure. |
| • | The VCM commands a D4 shift pattern. |
| • | The VCM freezes shift adapts from being updated. |
| • | The VCM stores DTC P1810 in VCM history during the second consecutive trip in which the conditions for setting the DTC are met. |
Conditions for Clearing the MIL/DTC
| • | The VCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes. |
| • | A scan tool clears the DTC from VCM history. |
| • | The VCM clears the DTC from VCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring. |
| • | The VCM cancels the DTC default actions when the fault no longer exists and the ignition switch is OFF long enough in order to power down the VCM. |
Diagnostic Aids
| • | Refer to Transmission Fluid Pressure (TFP) Manual Valve Position Switch Logic table for the normal range signals and the illegal combinations. On the table, ON is 0 volts, OFF is B+. |
| • | Inspect the wiring at the VCM, the transmission connector and all other circuit connecting points for the following conditions: |
| - | A backed out terminal |
| - | A damaged terminal |
| - | Reduced terminal tension |
| - | A chafed wire |
| - | A broken wire inside the insulation |
| - | Moisture intrusion |
| - | Corrosion |
| • | When diagnosing for an intermittent short or open condition, massage the wiring harness while watching the test equipment for a change. |
| • | Refer to the Transmission Fluid Pressure Manual Valve Position Switch Resistance Check or the Functional Test for further information. |
Gear Position | Range Signal A | Range Signal B | Range Signal C |
|---|---|---|---|
Park | OFF | ON | OFF |
Reverse | ON | ON | OFF |
Neutral | OFF | ON | OFF |
Overdrive | OFF | ON | ON |
Dr 3 | OFF | OFF | ON |
Dr 2 | OFF | OFF | OFF |
Low | ON | OFF | OFF |
Illegal | ON | OFF | ON |
Illegal | ON | ON | ON |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step compares the indicated range signal to the selected manual valve.
-
This step tests for correct voltage from the VCM to the transmission 20-way connector.
Step | Action | Value(s) | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check (4.3L) or Powertrain On Board Diagnostic (OBD) System Check (5.0L and 5.7L) in Engine Controls | |||||||||
2 | Perform the following inspections:
Did you perform the inspections? | -- | -- | |||||||||
Important: Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records. Using the Clear Info function erases the Freeze Frame and Failure Records from the VCM. Refer to the Transmission Fluid Pressure (TFP) Manual Valve Position Switch Logic table. Does each selected transmission range match the scan tool TFP Switch A/B/C display? | -- | Go to Diagnostic Aids | ||||||||||
Refer to Automatic Transmission Inline Harness Connector End View . Is B+ displayed on all three circuits? | -- | |||||||||||
5 | Inspect the circuits that did not indicate B+ for an open or a short to ground condition. Refer to General Electrical Diagnosis in Wiring Systems. Did you find an open or short to ground condition? | -- | ||||||||||
6 | Verify that circuits 1224 (PNK), 1225 (DK BLU) and 1226 (RED) are not shorted together. Use a fused jumper wire to ground on each circuit while monitoring the scan tool TFP Switch A/B/C display. When a range signal circuit is grounded, are any other range signal circuits affected? | -- | Go to the Transmission Fluid Pressure Manual Valve Position Switch Resistance Check . | |||||||||
7 | Replace the VCM. Refer to VCM Replacement/Programming (4.3L) or VCM Replacement/Programming (5.0L and 5.7L) in Engine Controls. Is the replacement complete? | -- | -- | |||||||||
8 | Repair the affected wiring as necessary. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- | |||||||||
9 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | -- | System OK |
