Mechanics

CHEVY TRANSMISSION

1996 Chevrolet Silverado

1996 Chevy Silverado V8 Four Wheel Drive Automatic 200000 miles

Shift vehicle in gears but does not move forward or backwards. Get OBDII code P1810, which is TFP valve position switch circuit. Is this a switch within the trans mission and does tranny have to be rebuild?
Avatar
Siggi
March 7, 2009.



P1810, TRANSMISSION FLUID PRESSURE (TFP) POSITION SWITCH ASSEMBLY MALFUNCTION Circuit Description Transmission Fluid Pressure (TFP) position switch assembly consists of 5 pressure switches and a Transmission Fluid Temperature (TFT) sensor. 2 switches are normally -closed. 3 other switches are normally -open. Complete assembly mounts on control valve body. PCM supplies battery voltage to each range switch. PCM grounds one or more range switch signal circuit through various combinations of pressure switches. PCM monitors combinations in order to detect what manual valve position has been selected. PCM compares actual voltage combination of switches to TFP position switch combination values stored in memory. TFP position switch cannot distinguish between Park and Neutral because monitored valve body pressures are identical. DTC P1810 detects an invalid state of TFP position switch. See TFP LOGIC TABLE .
NOTE: Perform OBD system check prior to performing diagnostic procedures. For wire terminal locations, see WIRING DIAGRAMS . Transmission Fluid Pressure (TFP) position switch assembly may also be referred to as Pressure Switch Assembly (PSA).
Page 1 of 3 DIAGNOSIS - 4L80-E -1996 Chevrolet Pickup K1500


http://www.2carpros.com/forum/automotive_pictures/62217_1810_1.jpg


Conditions For Setting DTC P1810 DTC will set when any one of the following 3 conditions occur: Condition No. 1: This condition detects an illegal switch combination.  System voltage is 10-17 volts  Engine is running.  PCM detects an illegal TFP state.  All conditions are met for 5 seconds.
Condition No. 2: This condition detects D2, D4 or Reverse during an engine start.  DTC P0502 (vehicle speed sensor) is not present.  Engine speed is less than 100 RPM for .3 seconds, then engine speed is between 100-600 RPM for .3 seconds, then engine speed is more than 600 RPM for 3 seconds.  Vehicle speed is less than 2 MPH.  Detected gear range is D2, D4 or Reverse.  All conditions are met for 3 seconds. Condition No. 3: This condition detect Park or Neutral when vehicle should be in D4.  DTC P0502 (vehicle speed sensor) is not present.  Engine speed is less than 2000 RPM.  Speed ratio (engine speed divided by output speed) is .39-.80.  TCC is locked on.  Detected gear range is Park or Neutral.  All conditions are met for 5 seconds. DTC P1810 will be stored in PCM history. MIL will glow after 2 consecutive trips with failure, PCM freezes shift adapts from being updated, line pressure defaults to D2 and shift pattern defaults to D4. Diagnostic Procedures 1. Check transmission fluid. Fill as needed. Ensure transmission shift linkage is adjusted correctly. Diagnose Transmission Fluid Pressure (TFP) position switch. Switch is also referred to as Pressure Switch Assembly (PSA). See COMPONENT TESTS . Connect scan tool to DLC. Turn ignition switch to ON position. DO NOT start engine. Using scan tool, record freeze frame and failure records for reference. Data will be lost when DTCs are cleared later in this test. 2. Start engine and let idle. Apply parking brake. While observing scan tool, shift transmission into each gear position. If gear position matches transmission range switch on scan tool, see DIAGNOSTIC AIDS. If gear position does not match transmission range switch on scan tool, go to next step. 3. Turn ignition off. Disconnect transmission 20-pin connector. Install Jumper Harness (J-39775) on PCM side of transmission 20-pin connector. Turn ignition switch to ON position. DO NOT start engine. Using a DVOM, measure voltage at range input circuits "A", "B" and "C" at transmission 20-pin connector. See WIRING DIAGRAMS . If battery voltage is present at all circuits, go to step 5. If battery voltage is not present at all circuits, go to next step. 4. Check each circuit which did not have battery voltage for open or short to ground. Repair circuit (s) as necessary, then go to step 6. If all circuits are okay, inspect wiring for poor connections at appropriate PCM connector. Check for possible bent, backed out, deformed or damaged terminals. Repair as necessary, then go to step 6. If connections and terminals are okay, replace PCM, thengo to step 6. 5. Ensure circuits are not shorted together. Use a fused jumper to separately ground each circuit while monitoring scan tool TFP position switch A/B/C display. Repair circuits as necessary, then go to next step. If all circuits are okay, diagnose Transmission Fluid Pressure (TFP) position switch. Switch is also referred to as Pressure Switch Assembly (PSA). See COMPONENT TESTS . 6. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Select "Specific DTC" and enter DTC "P1810". Turn ignition switch to ON position for at least 2 seconds. Start vehicle and idle for 5 seconds. Drive vehicle in D4 until TCC locks for 20 seconds. If DTC P1810 is not present, repair is complete. If DTC P1810 is still present, repeat test. Diagnostic Aids Inspect wiring for poor connections at PCM and at transmission 20-pin connector. Check for possible bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Also check for chafed wire that could short to bare metal or other wiring. Inspect for broken wire inside insulation. If diagnosing for possible intermittent short or open condition, move wiring harness while observing scan tool for value change.
These are on the valve body which is inside the pan, under the filer. Try inspection the connector for water or corosion at the connection first.

Merlin2021
Mar 8, 2009.