Automatic Transmission Diagnosis - 4l60-e Chevrolet Blazer S15

APPLICATION

4L60-E APPLICATION

DESCRIPTION

The 4L60-E transmission uses 2 electric shift solenoids to control transmission upshifts and downshifts. In addition, a pressure control (force motor) solenoid controls hydraulic line pressure, and a Torque Converter Clutch (TCC) solenoid controls TCC application. A TCC Pulse Width Modulated (PWM) solenoid is used to control fluid acting on converter clutch valve, which then controls TCC apply and release. A 3-2 control solenoid modulates hydraulic pressure for the 2-4 band and 3-4 clutch to improve 3-2 downshift. Solenoids are turned on and off by Powertrain Control Module (PCM) on passenger cars and trucks with 2.2L engine, or by Vehicle Control Module (VCM) on all other light trucks and vans.

PCM/VCM receives signals from various transmission sensors. Sensors include engine speed and throttle position, transmission speed, hydraulic pressure and transmission fluid temperature. PCM/VCM has on-board self-diagnostics to help identify any parts or circuits which may need further testing.

INTRODUCTION

Shift solenoid holds hydraulic pressure (solenoid on) or releases hydraulic pressure (solenoid off). This action controls shift valves inside valve body. By switching one or both solenoids on or off, different combinations of clutches, sprags and bands are operated. See CLUTCH & BAND APPLICATION under TROUBLE SHOOTING.

PCM/VCM

PCM is located under air cleaner on Caprice, Fleetwood, Impala SS and Roadmaster, at right rear corner of engine compartment on Camaro and Firebird, and above power brake booster on Corvette.

On light trucks and vans, VCM is located on left side of engine compartment on "C" and "K" series vehicles, on left side inner fender panel on "G" series vehicles, and on left side of engine compartment near battery on "L", "M", "S" and "T" series vehicles. For series identification, see BODY CODE in APPLICATION table.

PCM/VCM controls TCC, pressure control solenoid, (hydraulic pressure), PWM solenoid and shift solenoids 1-2 and 2-3. In addition, PCM/VCM also controls ignition, fuel and emission devices related to engine.

PCM/VCM receives electronic signals from sensors and switches. These signals help PCM/VCM determine when to operate various relays and solenoids related to engine and transmission components.

SENSORS & SWITCHES

PCM/VCM controls converter clutch lock-up, upshifts and downshifts based on transmission temperature, system voltage, throttle position, transmission oil pressure switches (5), and transmission output and input (engine) speed sensors. (Scheme 35) System includes several other sensors and switches that are used for engine control (gasoline engines). For additional information and testing of engine components, see appropriate SYSTEM/COMPONENT TESTS article in ENGINE PERFORMANCE section.

Shift Solenoids 1-2 & 2-3

Transmission is shifted up or down by 2 electric shift solenoids. Both solenoids are located on valve body. (Scheme 35) Ignition power is supplied to each solenoid by transmission fuse. Solenoid 1-2 controls hydraulic pressure to 1-2 shift valve. Solenoid 2-3 controls hydraulic pressure to 2-3 shift valve.

Note. The 3-4 shift valve is directly controlled by hydraulic circuits in valve body.

Pressure Control Solenoid

Pressure control (force motor) solenoid has a spool valve and operates pressure regulator valve. (Scheme 35) PCM/VCM sends a frequency signal to pressure control solenoid to regulate hydraulic line pressure. Frequency signal (duty cycle) is measured with a dwell meter or lab scope. When duty cycle is zero, line pressure is at maximum, and pressure control solenoid draws zero amps. When duty cycle is 60 percent, line pressure is at minimum, and pressure control solenoid draws 1.1 amps at 4.5 volts.

Locating Transmission Solenoids, Sensors & Switches Courtesy of General Motors Corp. Scheme 35

TCC Solenoid

This solenoid is used to control TCC apply valve. PCM/VCM sends a frequency signal to TCC solenoid to gradually apply or release TCC. (Scheme 35)

3-2 Control Solenoid

The 3-2 shift solenoid valve assembly is an ON/OFF solenoid that is used in order to improve the 3-2 downshift. The solenoid regulates the release of the 3-4 clutch and the 2-4 band apply. If a voltage fault is detected in the 3-2 shift solenoid circuit, diagnostic trouble code P0785 will set.

Note. The 3-2 shift solenoid valve assembly resistance should be a minimum of 20-24 ohms at 68°F (20°C).

TCC PWM Solenoid

TCC PWM solenoid is used to control fluid acting on converter clutch valve, which then controls TCC apply and release. (Scheme 35) TCC PWM solenoid is used to provide smooth engagement of torque converter clutch by operating with a duty cycle on time of less than 50 percent.

SELF-DIAGNOSTICS

PCM/VCM constantly monitors all electrical circuits. If PCM/VCM detects circuit problems or sensors out of range, it will record a Diagnostic Trouble Code (DTC). If problem continues for a predetermined time, Malfunction Indicator Light (MIL) will glow.

If MIL is on all the time, DTC(s) are currently being detected. If MIL is off, but PCM/VCM had detected a circuit or sensor problem, DTC(s) will be stored in computer memory.

Stored DTCs may be retrieved from PCM/VCM memory using a factory recommended Tech 1 scan tool or aftermarket scan tool. DTCs CANNOT be retrieved by grounding 16-pin Data Link Connector (DLC).

Note. Faulty engine sensors and actuators may cause transmission related DTCs or driveability problems. Engine faults and related DTCs must be diagnosed and repaired before transmission codes are repaired. For additional information on diagnosing and repairing engine related PCM/VCM trouble codes, see appropriate TESTS W/CODES in ENGINE PERFORMANCE section.

TROUBLE SHOOTING

Note. For trouble shooting procedures, see TROUBLE SHOOTING in the AUTO TRANS OVERHAUL - 4L60-E article.

CLUTCH & BAND APPLICATION

CLUTCH & BAND APPLICATION CHART (4L60-E)

ELECTRONIC SELF-DIAGNOSTICS

Note. To test electronic control of transmission solenoids without using self-diagnostics or if self-diagnostics does not function, go to COMPONENT TESTS under ELECTRONIC TESTING. After repairs are made, DTCs should be erased from computer memory. See CLEARING TROUBLE CODES under ELECTRONIC SELF-DIAGNOSTICS.

Note. Trouble codes will be recorded at various operating times. Some codes require operation of affected sensor or switch for 5 seconds; others may require operation for 5 minutes or longer at normal operating temperature, road speed and load. Therefore, some codes may not set in a service bay operational mode and may require road testing vehicle in order to duplicate condition under which code will set.

RETRIEVING CODES

Note. Stored DTCs may be retrieved from PCM/VCM memory using a factory recommended Tech 1 scan tool or aftermarket scan tool. DTCs CANNOT be retrieved by grounding 16-pin Data Link Connector (DLC). Plugging scan tool into DLC, located under instrument panel, enables user to read DTCs and check voltages in system on serial data line.

Scan tools may also furnish information on status of output devices (solenoids and relays). However, status parameters are only an indication that output signals have been sent to devices by control module; they do not indicate if devices have responded properly to signal. Check for proper response at output device using a voltmeter or test light.

If trouble codes are not present, this is not necessarily an indication a problem does not exist. Driveability related problems with codes displayed occur about 20 percent of the time, while driveability problems without codes occur about 80 percent of the time. Sensors that are out of specification WILL NOT set a trouble code but WILL cause driveability problems. Using scan tool is the easiest method of checking sensor specifications and other data parameters. Scan tool is also useful in finding intermittent wiring problems by wiggling wiring harness and connections (key on, engine off) while observing scan tool.

TROUBLE CODE DEFINITIONS

Note. Only transmission-related trouble codes are listed. For engine-related DTCs, see appropriate TESTS W/CODES article in ENGINE PERFORMANCE section. Engine related DTCs must be repaired first, as engine performance and related component signals will affect transmission operation and diagnosis.

PCM/VCM TROUBLE CODE DEFINITIONS (CARS)

PCM/VCM TROUBLE CODE DEFINITIONS (TRUCKS)

HARD OR INTERMITTENT TROUBLE CODE DETERMINATION

Note. During any diagnostic procedure, it must be determined if codes are hard failure codes or intermittent failure codes. Diagnostic tests will not usually help analyze intermittent codes. To determine hard codes and intermittent codes, proceed as follows

1. Enter diagnostic mode. See «RETRIEVING CODES»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e__retrieving-codes) . Read and record all stored DTCs. Exit diagnostic mode and clear trouble codes. See «CLEARING TROUBLE CODES»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e__clearing-trouble-codes) .
2. Apply parking brake and place transmission in Neutral or Park. Block drive wheels and start engine. MIL should go out. Run warm engine at specified curb idle for 2 minutes and note MIL.
3. If MIL comes on, enter diagnostic mode. Read and record DTCs. This will reveal hard failure codes. DTCs may require a road test to reset hard failure after clearing DTCs. If MIL does not come on, all stored DTCs were intermittent failures.

CLEARING TROUBLE CODES

DTCs can be cleared using scan tool. If scan tool is not available, turn ignition switch to OFF position. Remove control module fuse from fuse block for 30 seconds. Replace fuse. If fuse cannot be located, disconnect PCM/VCM pigtail at battery for 30 seconds. Codes may also be cleared by disconnecting negative battery cable. However, this may result in loss of other on-board memory data, such as preset radio tuning. After power to PCM/VCM is removed, poor driveability may occur until control module "relearns" operating parameters.

DTCs will also be cleared under the following conditions: PCM/VCM will turn off MIL after 3 consecutive ignition cycles without a failure reported. PCM/VCM will cancel DTC default actions when fault no longer exists and ignition is cycled off long enough to power down PCM/VCM. DTC will be cleared when vehicle has achieved 40 warm-up cycles without a failure reported.

Note. Not all DTCs are applicable to all models.

Diagnostic Tests

Following diagnostic tests are DTC specific. Always perform On-Board Diagnostic (OBD) System Check prior to performing any diagnostic procedure. For terminal locations, see WIRING DIAGRAMS . For engine-related DTCs, see appropriate TESTS W/CODES article in ENGINE PERFORMANCE section.

Diagnostic Aids

Diagnostic aids located at end of each diagnostic test, are additional tips used to help diagnose trouble codes when diagnostic procedures do not find a problem.

USING DIAGNOSTIC TESTS & WIRING DIAGRAMS

PCM connector colors and terminal identification may vary with vehicle model and engine size. When using following diagnostic tests, see appropriate wiring diagram to determine which PCM connector(s) to disconnect during test procedure. Locate component being tested and trace specified wiring circuit to determine PCM connector and terminal related to that component.

ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK

Note. Use of Tech 1 scan tool is required to perform OBD system check. Perform this test prior to performing any diagnostic procedures in DTC tests.

The OBD System Check determines

1. If Malfunction Indicator Light (MIL) works.
2. If PCM is operating and can recognize a fault.
3. If any codes are stored.

OBD system check is the starting point for utilizing the self-diagnostic system for determining computer-related problems. After performing necessary tests as described in diagnostic system check, if no codes are indicated and driveability problems still exist, see appropriate TESTS W/O CODES article in ENGINE PERFORMANCE section.

Note. The following steps should be performed first to reduce diagnostic time and prevent replacement of good parts.

3.8L

1. Turn ignition on with engine off. Observe Malfunction Indicator Light (MIL). If MIL lights, go to next step. If MIL does not light, go to A-1, MIL INOPERATIVE under «BASIC TESTING - 3.8L»(ref-20278) article in ENGINE PERFORMANCE section.
2. Turn ignition off. Install scan tool and follow scan tool manufacturer's instructions to proceed with test. Turn ignition on. If scan tool displays PCM data, go to next step. If scan tool does not display PCM data, go to A-2, NO SCAN TOOL DATA in «BASIC TESTING - 3.8L»(ref-20278) article in ENGINE PERFORMANCE section.
3. Attempt to start engine. If engine starts and runs, go to next step. If engine does not start or starts and dies, go to NO START DIAGNOSIS (A-3) in «BASIC TESTING - 3.8L»(ref-20278) article in ENGINE PERFORMANCE section.
4. Using scan tool, observe DTC statuses; MIL REQUEST, FAIL THIS IGN, LAST TST FAIL and HISTORY. If any of these DTC status are present, refer to affected DTC to diagnose problem. If DTC(s) are not present, check related circuit or component(s). See appropriate SYSTEM/COMPONENT TESTS article in ENGINE PERFORMANCE section.

4.3L & 5.7L

1. Install scan tool and follow scan tool manufacturer's instructions to proceed with test. Turn ignition on. If scan tool displays PCM data, go to next step. If scan tool does not display PCM data, go to NO SCAN TOOL DATA under appropriate BASIC TESTING article in ENGINE PERFORMANCE section. Refer to the following menu
2. Attempt to start engine. If engine starts and runs, go to next step. If engine does not start or starts and dies, go to ENGINE CRANKS BUT DOES NOT RUN under appropriate BASIC TESTING article in ENGINE PERFORMANCE section.
3. Using scan tool, select ENG DTC, DTC INFO and LAST TST FAIL. If any DTCs are present, go to next step. If DTCs are not present, select ENG DTC, DTC INFO and HISTORY. If any DTCs are present, go to next step. If DTCs are not present, go to step 5.
4. Using scan tool, select CAPTURE INFO, then STORE INFO (this option will only be displayed if there is no previously captured data) or REFRESH INFO (to overwrite older data with current info). Then refer to affected DTC to diagnose problem.
5. If DTCs are not present, compare scan tool data with specific component values. If values are not within specified range, check related circuit or component(s). See appropriate SYSTEM/COMPONENT TESTS article in ENGINE PERFORMANCE section. Refer to the following menu

P0502, VEHICLE SPEED SENSOR CIRCUIT (LOW INPUT)

Note. Perform OBD system check prior to performing diagnostic procedures. For wire circuit identification, see WIRING DIAGRAMS .

Circuit Description

Vehicle speed is signaled to PCM by Vehicle Speed Sensor (VSS). Sensor is a Permanent Magnet (PM) generator mounted to transmission case extension. PM generator produces an AC voltage as speed sensor rotor teeth pass sensor's magnetic field. PCM converts AC voltage into digital signal. PCM uses vehicle speed to determine shift timing and TCC apply and release. VSS resistance value is 1480-2700 ohms. DTC P0502 detects a low vehicle output speed when vehicle has high engine speed in drive gear.

Conditions For Setting DTC P0502

DTC will set under the following conditions

1. Transmission is not in Park or Neutral.
2. DTCs P0107 and P0108 (MAP sensor), or P0122 and P0123 (throttle position) are not present.
3. DTC P1810 (transmission fluid pressure position switch) is not present.
4. Engine speed is 3000-5500 RPM.
5. Throttle angle is more than 17 percent.
6. Output speed is less than 250 RPM.
7. All conditions are met for 3 seconds.

DTC P0502 will be stored in PCM history. MIL will light at first failure signal. PCM commands 2nd gear only, inhibits TCC solenoid engagement, freezes shift adapts from being updated and commands maximum line pressure.

Diagnostic Procedures

1. 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. Raise and support vehicle.
2. Start engine and let idle. Disable traction control system (if equipped). Shift gear selector to any forward position. Select "Output Speed" on scan tool. With drive wheels rotating, if transmission output speed does not increase when wheel speed increases, go to next step. If transmission output speed increases when wheel speed increases, see DIAGNOSTIC AIDS below.
3. Turn ignition off. Disconnect appropriate PCM connector connected to VSS. See «WIRING DIAGRAMS»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e) . Connect voltmeter between VSS terminals at appropriate PCM connector terminals. Rotate drive wheels and observe voltmeter display. If voltage is less than .5 volt, go to next step. If voltage is more than .5 volt, check PCM connector for damaged or backed out connector terminals, weak terminal tension and poor connections. Repair as necessary, then go to step 7. If terminals and connections are okay, replace PCM, then go to step 7.
4. Using an ohmmeter, measure resistance between VSS terminals at appropriate PCM connector. See «WIRING DIAGRAMS»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e) . If resistance is more than 2700 ohms, check for poor connection or open circuit in VSS wiring. Repair as necessary, then go to step 7. If wiring is okay, go to next step. If resistance is more than 1480 ohms, go to next step. If resistance is less than 1480 ohms, check for short to ground, or for VSS wires shorted together. Repair as necessary, then go to step 7. If wiring is okay, go to next step.
5. Reconnect appropriate PCM connector. Disconnect VSS connector. Measure resistance between VSS terminals. If resistance is not 1480-2700 ohms, go to next step. If resistance is 1480-2700 ohms, check PCM connector for damaged or backed out connector terminals, weak terminal tension and poor connections. Repair as necessary, then go to step 7. If terminals and connections are okay, replace PCM, then go to step 7.
6. Remove VSS from transmission. Inspect output speed sensor rotor for damage or misalignment. Repair as necessary, then go to next step. If rotor is okay, replace VSS, then go to next step.
7. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Select "Specific DTC" and enter DTC "P0502". Test drive vehicle. Ensure transmission output speed is more than 251 RPM for 2 seconds. If DTC P0502 is not present, repair is complete. If DTC P0502 is still present, repeat test.

DTC P0502 sets when no vehicle speed is detected at start-off. Check for Electromagnetic Interferences (EMI) induced on VSS circuits. Check for bent, backed out or broken terminals, or misaligned connectors. Inspect for damaged VSS or for damaged output speed sensor rotor teeth. Ensure VSS is aligned correctly and secured to transmission case properly. An incorrect calibration may set DTC P0502. If diagnosing for possible intermittent short or open condition, move wiring harness while observing scan tool for value change.

P0560, SYSTEM VOLTAGE MALFUNCTION

Note. Perform OBD system check prior to performing diagnostic procedures. For wire circuit identification, see WIRING DIAGRAMS .

PCM monitors fused battery and ignition voltage circuits for low or high system voltage.

Conditions For Setting DTC P0560

DTC will set under the following conditions

1. For low system voltage, engine speed is more than 1000 RPM and system voltage is less than 10 volts at a maximum transmission temperature of 302°F (150°C), or less than 7.3 volts at a minimum transmission temperature of -40°F (-40°C).
2. For high system voltage, system voltage is more than 17 volts for 2 seconds.
3. All conditions are met for 4 seconds.

DTC P0560 will be stored in PCM history. MIL will NOT light. PCM will freeze shift adapts from being updated. All transmission output devices are off except TCC PWM solenoid and 3-2 shift solenoid.

1. 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. Using a DVOM, measure and record battery voltage at battery. If voltage is more than 10.5 volts, go to next step. If voltage is less than 10.5 volts, diagnose battery condition and repair or replace as necessary.
3. Start engine and warm to normal operating temperature. If generator (CHECK ENGINE) light on instrument panel is on, diagnose charging system and repair as necessary. If generator (CHECK ENGINE) light is off, increase engine speed to 1000-1500 RPM. Observe scan tool system voltage. If system voltage is 12-15 volts, go to next step. If system voltage is not 12-15 volts, diagnose charging system and repair as necessary.
4. Turn engine off. Disconnect appropriate PCM connector connected to battery positive voltage circuit. See «WIRING DIAGRAMS»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e) . Turn ignition switch to ON position. DO NOT start engine. Using a DVOM, check for battery voltage at battery positive voltage terminals of appropriate PCM connector.
5. If difference between measured battery voltage in step 2 and voltage measured at appropriate PCM connector is less than .5 volt, go to next step. If voltage is more than .5 volt, check for high resistance in battery positive voltage circuits. Repair as necessary, then go to step 7.
6. Disconnect appropriate PCM connector connected to ignition positive voltage circuit. See «WIRING DIAGRAMS»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e) . Using a DVOM, check for ignition voltage at ignition positive voltage terminals of appropriate PCM connector. If difference between measured battery voltage in step 2 and voltage measured at appropriate PCM connector is more than .5 volt, check for high resistance in ignition voltage circuits. Repair as necessary, then go to next step. If voltage is less than .5 volt, check appropriate PCM connector for bent, backed out or damaged connector terminals. Repair as necessary, then go to next step. If connector terminals are okay, replace PCM, then go to next step.
7. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Select "Specific DTC" and enter DTC "P0560". Start vehicle and warm to normal operating temperature. PCM must detect a system voltage of 10-16 volts. If DTC P0560 is not present, repair is complete. If DTC P0560 is still present, repeat test.

Charging battery with battery charger or jump starting vehicle could set DTC P0560. If DTC set when accessories are operated, check for poor system connections or excessive current draw. Inspect starter solenoid for faulty connection. Inspect starter solenoid fusible link. Check drive belt for wear or incorrect tension.

P0712, TRANS. FLUID TEMPERATURE (TFT) SENSOR CIRCUIT (LOW INPUT)

Note. Perform OBD system check prior to performing diagnostic procedures. For wire circuit identification, see WIRING DIAGRAMS.

Transmission Fluid Temperature (TFT) sensor is a negative coefficient thermistor within Transmission Fluid Pressure (TFP) position switch. TFP is also referred to as Pressure Switch Assembly (PSA). TFT sensor controls signal voltage from PCM. PCM provides a 5 volt reference to sensor on TFT sensor signal circuit. When transmission fluid is cold, sensor resistance is high, and PCM detects high signal voltage. As transmission fluid temperature increases, sensor resistance decreases and voltage decreases. At normal operating temperature of 212°F (100°C), voltage is about 1.5-2 volts. Check sensor for shifted calibration by using sensor TEMPERATURE-TO-RESISTANCE VALUES table. DTC P0712 detects a continuous short to ground in TFT sensor signal circuit or TFT sensor.

Conditions For Setting DTC P0712

DTC will set under the following conditions

1. System voltage is 10-17 volts.
2. Ignition switch is in ON position.
3. TFT sensor indicates a voltage less than .196 volt.
4. All conditions are met for 10 seconds.

PCM turns on MIL after 2 consecutive trips with failure. Transmission default temperature is 275°F (135°C). PCM freezes shift adapts from being updated.

Diagnostic Procedure

1. Ensure transmission fluid level is correct. 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. Read TFT sensor signal voltage on scan tool. If TFT sensor signal voltage is less than .196 volt, go to next step. If TFT sensor signal voltage is more than .196 volt, see DIAGNOSTIC AIDS below.
3. Turn ignition off. Disconnect transmission 20-pin connector. Turn ignition switch to ON position. DO NOT start engine. If TFT sensor signal voltage is 4.92 volts, go to next step. If TFT sensor signal voltage is not 4.92 volts, check for short to ground in TFT sensor signal circuit. Repair circuit as necessary, then go to step 7. If circuit is okay, go to step 6.
4. Install Jumper Harness (J-39775) on transmission side of 20-pin connector. Using a DVOM, measure resistance of TFT sensor between TFP position switch terminals of jumper harness. If resistance is 3088-3941 ohms, see DIAGNOSTIC AIDS below.
5. If resistance is not 3088-3941 ohms, remove transmission oil pan. Check for short to ground in transmission wiring harness. Repair as necessary. If wiring harness is okay, disconnect TFT sensor connector. Measure resistance between TFT sensor terminals. If resistance is 3088-3941 ohms, see DIAGNOSTIC AIDS below. If resistance is not 3088-3941 ohms, replace TFP position switch, then go to step 7.
6. Check PCM connector for damaged or backed out connector terminals, weak terminal tension and poor connections. Repair as necessary, then go to next step. If terminals and connections are okay, replace PCM, then go to next step.
7. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Select "Specific DTC" and enter DTC "P0712". Ensure TFT sensor indicates a voltage more than .33 volt for 2 seconds. If DTC P0712 is not present, repair is complete. If DTC P0712 is still present, repeat test.

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. Check for chafed wire that could short to bare metal or other wiring. Check for broken wire inside insulation. If diagnosing for possible intermittent short or open condition, move wiring harness while observing scan tool for value change. If DTC P1812 is also set, check transmission cooling system for possible blockage and/or restrictions.

TEMPERATURE-TO-RESISTANCE VALUES

P0713, TRANS. FLUID TEMPERATURE (TFT) SENSOR CIRCUIT (HIGH INPUT)

Note. Perform OBD system check prior to performing diagnostic procedures. For wire circuit identification, see WIRING DIAGRAMS.

Transmission Fluid Temperature (TFT) sensor is a negative coefficient thermistor within Transmission Fluid Pressure (TFP) position switch. TFT sensor controls signal voltage from PCM. PCM provides a 5 volt reference to sensor on TFT sensor signal circuit. When transmission fluid is cold, sensor resistance is high, and PCM detects high signal voltage. As transmission fluid temperature increases, sensor resistance decreases and voltage decreases. At normal operating temperature of 212°F (100°C), voltage is about 1.5-2 volts. Check sensor for shifted calibration by using sensor TEMPERATURE-TO-RESISTANCE VALUES table. DTC P0713 detects a continuous open or short to voltage in TFT sensor signal circuit or TFT sensor.

Conditions For Setting DTC P0713

DTC will set under the following conditions

1. System voltage is 10-17 volts.
2. Ignition switch is in ON position.
3. TFT sensor indicates a voltage less than 4.94 volts.
4. All conditions are met for 50 seconds.

PCM turns on MIL after 2 consecutive trips with failure. Transmission default temperature is 275°F (135°C). PCM freezes shift adapts from being updated.

1. Ensure transmission fluid level is correct. 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. Read TFT sensor signal voltage on scan tool. If TFT sensor signal voltage is more than 4.92 volts, go to next step. If TFT sensor signal voltage is less than 4.92 volts, see DIAGNOSTIC AIDS below.
3. Turn ignition off. Disconnect transmission 20-pin connector. Install Jumper Harness (J-39775) on engine side of transmission 20-pin connector. Install fused jumper wire between appropriate PCM connector TFT sensor ground terminal, and appropriate PCM connector TFT sensor signal terminal of jumper harness. See WIRING DIAGRAMS. Turn ignition switch to ON position. DO NOT start engine. If TFT sensor signal voltage is less than .196 volt, go to next step. If TFT sensor signal voltage is more than .196 volt, check for open or short to voltage in TFT sensor signal circuit, or for open in TFT ground circuit. Repair circuits as necessary, then go to step 7. If circuits are is okay, go to step 6.
4. Turn ignition off. Remove jumper wire. Disconnect jumper harness from engine side of 20-pin connector. Install jumper harness on transmission side of 20-pin connector. Using a DVOM, measure resistance of TFT sensor harness between TFP position switch terminals of jumper harness. If resistance is 3088-3941 ohms, see DIAGNOSTIC AIDS below.
5. If resistance is not 3088-3941 ohms, remove transmission oil pan. Check for open in transmission wiring harness. Repair as necessary, then go to step 7. If wiring harness is okay, disconnect TFT sensor connector. Measure resistance between TFT sensor terminals. If resistance is 3088-3941 ohms, see DIAGNOSTIC AIDS below. If resistance is not 3088-3941 ohms, replace TFP position switch, then go to step 7.
6. Check PCM connector for damaged or backed out connector terminals, weak terminal tension and poor connections. Repair as necessary, then go to next step. If terminals and connections are okay, replace PCM, then go to next step.
7. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Select "Specific DTC" and enter DTC "P0713". Ensure TFT sensor indicates a voltage less than 4.92 volts for 2 seconds. If DTC P0713 is not present, repair is complete. If DTC P0713 is still present, repeat test.

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. Check for chafed wire that could short to bare metal or other wiring. Check for broken wire inside insulation. If diagnosing for possible intermittent short or open condition, move wiring harness while observing scan tool for value change. Check engine and transmission harness for open condition.

TEMPERATURE-TO-RESISTANCE VALUES

P0719, BRAKE SWITCH CIRCUIT LOW INPUT (SWITCH STUCK ON)

Note. Perform OBD system check prior to performing diagnostic procedures. For wire circuit identification, see WIRING DIAGRAMS.

Torque Converter Clutch (TCC) brake switch is used to indicate brake pedal status to PCM. PCM de-energizes TCC solenoid when brake pedal is applied. DTC P0719 detects an open (stuck on) brake switch during acceleration.

Conditions For Setting DTC P0719

DTC will set under the following conditions

1. P0502 (vehicle speed sensor) is not present.
2. Vehicle speed is less than 5 MPH.
3. Then vehicle speed is 5-20 MPH for 6 seconds, then vehicle speed is more than 20 MPH for 4 seconds.
4. All conditions must occur 7 times with brake switch on for more than 15 minutes without PCM detecting voltage input of 2 seconds or more.

MIL will light after first failure signal. TCC brake switch remains closed with brake pedal released, PCM inhibits engagement of TCC solenoid, inhibits 4th gear if in hot mode and freezes shift adapts from being updated.

1. 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. If an ABS code is set, inspect applicable fuse and replace as necessary. Apply and release brake pedal while observing scan tool. If scan tool displays brake pedal in correct positions, see DIAGNOSTIC AIDS below. If scan tool does not display brake pedal in correct positions, go to next step.
3. Connect test light between ground and ignition feed circuit terminal at brake switch. If test light is off, repair open in ignition feed circuit, then go to step 9. If test light is on, connect test light between ground and brake switch signal terminal at brake switch. If test light is off, go to step 5. If test light is on, go to next step.
4. Apply brake pedal. If test light is off, go to step 6. If test light is on, check brake switch signal circuit for short to voltage. Repair circuit as necessary, then go to step 9. If circuit is okay, go to next step.
5. Ensure brake switch assembly is adjusted properly. Adjust brake switch as necessary, then go to step 9. If adjustment is okay, replace brake switch, then go to step 9.
6. Release brake pedal. Turn ignition off. Disconnect appropriate PCM connector connected to brake switch signal circuit. See «WIRING DIAGRAMS»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e) . Turn ignition switch to ON position. DO NOT start engine. Connect test light between ground and brake switch signal terminal of appropriate PCM connector. If test light is on, go to next step. If test light is off, check for open in brake switch signal circuit between brake switch and PCM. Repair as necessary, then go to step 9.
7. Turn ignition off. Reconnect appropriate PCM connector. Turn ignition switch to ON position. DO NOT start engine. Apply and release brake pedal. If scan tool displays brake pedal in correct positions, see DIAGNOSTIC AIDS below. If scan tool does not display brake pedal in correct positions, go to next step.
8. Check PCM connector for damaged or backed out connector terminals, weak terminal tension and poor connections. Repair as necessary, then go to next step. If terminals and connections are okay, replace PCM, then go to next step.
9. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Select "Specific DTC" and enter DTC "P0719". Ensure TCC brake switch signal indicates zero volts for 2 seconds with brake pedal applied. If DTC P0719 is not present, repair is complete. If DTC P0719 is still present, repeat test.

Check TCC brake switch for proper adjustment. Check PCM calibration for current update. Inspect wiring for poor connections at PCM. Check for possible bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wire that could short to bare metal or other wiring. Check for broken wire inside insulation. If diagnosing for possible intermittent short or open condition, move wiring harness while observing scan tool for value change.

P0724, BRAKE SWITCH CIRCUIT HIGH INPUT (SWITCH STUCK OFF)

Note. Perform OBD system check prior to performing diagnostic procedures. For wire circuit identification, see WIRING DIAGRAMS.

Torque Converter Clutch (TCC) brake switch is used to indicate brake pedal status to PCM. PCM de-energizes TCC solenoid when brake pedal is applied. DTC P0724 detects a closed (stuck off) brake switch during deceleration.

Conditions For Setting DTC P0724

DTC will set under the following conditions

1. P0502 (vehicle speed sensor) is not present.
2. PCM detects a closed TCC brake switch for 2 seconds and the following events occur 7 consecutive times
3. Vehicle speed is more than 20 MPH for 6 seconds.
4. Then vehicle speed is 5-20 MPH for 6 seconds, then vehicle speed is less than 5 MPH.

DTC P0724 will be stored in PCM history. MIL will NOT light. PCM freezes shift adapts from being updated.

1. 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. Apply and release brake pedal while observing scan tool. If scan tool displays brake pedal in correct positions, see DIAGNOSTIC AIDS below. If scan tool does not display brake pedal in correct positions, go to next step.
3. Connect test light between ground and ignition feed circuit terminal at brake switch. If test light is off, repair open in ignition feed circuit, then go to step 8. If test light is on, connect test light between ground and brake switch signal terminal at brake switch. If test light is off, go to step 5. If test light is on, go to next step.
4. Apply brake pedal. If test light is off, go to step 6. If test light is on, check brake switch signal circuit for short to voltage. Repair circuit as necessary, then go to step 8. If circuit is okay, go to next step.
5. Ensure brake switch assembly is adjusted properly. Adjust brake switch as necessary, then go to step 8. If adjustment is okay, replace brake switch, then go to step 8.
6. Apply and release brake pedal. If scan tool displays brake pedal in correct positions, see DIAGNOSTIC AIDS below. If scan tool does not display brake pedal in correct positions, go to next step.
7. Check PCM connector for damaged or backed out connector terminals, weak terminal tension and poor connections. Repair as necessary, then go to next step. If terminals and connections are okay, replace PCM, then go to next step.
8. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Select "Specific DTC" and enter DTC "P0724". Ensure TCC brake switch signal indicates 12 volts for 2 seconds with brake pedal released. If DTC P0724 is not present, repair is complete. If DTC P0724 is still present, repeat test.

Check TCC brake switch for proper adjustment. Check PCM calibration for current update. Inspect wiring for poor connections at PCM. Check for possible bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wire that could short to bare metal or other wiring. Check for broken wire inside insulation. If diagnosing for possible intermittent short or open condition, move wiring harness while observing scan tool for value change.

P0742, TCC STUCK ON

Note. Perform OBD system check prior to performing diagnostic procedures. For wire circuit identification, see WIRING DIAGRAMS. For fluid circuit identification, see OIL CIRCUIT DIAGRAMS in section No. 1.

Torque Converter Clutch (TCC) solenoid stops converter signal oil exhaust. PCM commands solenoid on and off through ground circuit. When TCC solenoid is de-energized, solenoid will release fluid and release TCC. DTC P0742 detects a low torque converter slip when TCC is off.

Conditions For Setting DTC P0742

DTC will set under the following conditions

1. P0122 or P0123 (throttle position sensor) is not present.
2. P0502 (vehicle speed sensor) is not present.
3. P1810 (TFP position switch) is not present.
4. P1860 (TCC PWM solenoid) is not present.
5. P1864 (TCC solenoid) is not present.
6. Throttle position is more than 13 percent.
7. Engine speed is more than 450 RPM and less than 5500 RPM for more than 2 seconds.
8. Commanded gear is not 1st.
9. TCC is commanded off.
10. Gear range is D4, D3 or D2.
11. TCC slip speed is -20 to 20 RPM for more than 5.6 seconds.

DTC P0742 will be stored in PCM history. MIL will light at first failure signal. PCM freezes shift adapts from being updated.

1. 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. Using scan tool, verify TP sensor value is within .6-5.0 volts. If TP sensor voltage is as specified, go to next step. If TP sensor voltage is not as specified, see DIAGNOSTIC AIDS below.
3. Drive vehicle in D4 range in 4th gear under steady acceleration with TP angle more than 25 percent. Select "TCC Solenoid" state on scan tool. If scan tool displays TCC slip speed of -20 to 20 RPM in off state, go to next step. If scan tool does not display TCC slip speed of -20 to 20 RPM in off state, see DIAGNOSTIC AIDS below.
4. TCC is mechanically stuck on. Inspect TCC for a clogged exhaust orifice in TCC solenoid, converter clutch apply valve stuck in apply position, misaligned or damaged valve body gasket, or a restricted release passage. Repair component as necessary, then go to next step.
5. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Hold throttle angle at 25 percent. Accelerate vehicle to 55 MPH. If throttle moves more than 3 percent, stop vehicle and start again. Ensure TCC slip speed is between -50 to 2500 RPM for 10 seconds with TCC off. Select "Specific DTC" and enter DTC "P0742". If DTC P0742 is not present, repair is complete. If DTC P0742 is still present, repeat test.

TCC may mechanically stick on with parking brake applied and any gear range selected. TCC fluid will mechanically apply TCC, which may cause engine to stall. A stuck TP sensor will set DTC P0742.

P0748, PRESSURE CONTROL SOLENOID ELECTRICAL MALFUNCTION

Note. Perform OBD system check prior to performing diagnostic procedures. For wire circuit identification, see WIRING DIAGRAMS.

Pressure Control Solenoid (PCS) is used to regulate transmission line pressure. PCM compares TP voltage, engine RPM and other inputs to determine appropriate line pressure for given load. PCM will regulate pressure by applying varying amperage to PCS. Applied amperage can vary from 0.1-1.0 amps. PCM then monitors amperage. DTC P0748 detects a continuous open or short to ground in PCS circuit.

Conditions For Setting DTC P0748

DTC will set under the following conditions

1. System voltage is 10-17 volts.
2. PCM recognizes PCS has reached electrical high or low limit.

DTC P0748 will be stored in PCM history. MIL will NOT light. PCM freezes shift adapts from being updated.

1. 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. Using scan tool, apply 0.1-1.0 amp and observe scan tool display. If PCS actual amperage reading is not within 0.16 amps of desired reference amperage reading, go to next step. If PCS actual amperage reading is within 0.16 amps of desired reference amperage reading, see DIAGNOSTIC AIDS below.
3. Turn ignition off. Disconnect transmission 20-pin connector. Install Jumper Harness (J-39885) to transmission side of 20-pin connector. Using an ohmmeter, measure resistance of PCS between PCS terminals of jumper harness. If resistance is 3-7 ohms, go to step 5.
4. If resistance is not 3-7 ohms, remove transmission oil pan. Disconnect PCS connector. Measure resistance between PCS terminals. If resistance is 3-7 ohms, check for open in PCS wiring harness. Repair wiring as necessary, then go to step 6. If resistance is not 3-7 ohms, replace PCS, then go to step 6.
5. Check PCS circuits for poor connection, open or short to ground. Repair circuits as necessary, then go to next step. If circuits are okay, check for damaged or backed out PCM connector terminals. Repair as necessary, then go to next step. If connector terminals are okay, replace PCM, then go to next step.
6. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Ensure duty cycle is not at low or high limit. Select "Specific DTC" and enter DTC "P0748". If DTC P0748 is not present, repair is complete. If DTC P0748 is still present, repeat test.

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. Check for chafed wire that could short to bare metal or other wiring. Check for broken wire inside insulation. If diagnosing for possible intermittent short or open condition, move wiring harness while observing scan tool for value change.

P0751, 1-2 SHIFT SOLENOID ("A") PERFORMANCE MALFUNCTION

Note. Perform OBD system check prior to performing diagnostic procedures. For wire circuit identification, see WIRING DIAGRAMS.

The 1-2 shift solenoid (solenoid "A") is a normally open exhaust valve that is used in conjunction with 2-3 shift solenoid (solenoid "B"), to allow 4 different shifting combinations. Solenoid is attached to control valve body. DTC P0751 detects a 1-1-4-4 or a 2-2-3-3 shift pattern, depending on mechanical failure.

Conditions For Setting DTC P0751

DTC will set under the following conditions

1. DTCs P0122 or P0123 (throttle position) are not present.
2. DTC P0502 (vehicle speed sensor) is not present.
3. DTC P0742 (TCC stuck on) is not present.
4. DTCs P0753 and P0758 (1-2 and 2-3 shift solenoid electrical) are not present.
5. DTC P1810 (Temperature Fluid Pressure position switch) is not present.
6. DTC P1886 (3-2 shift solenoid) is not present.
7. Gear range is D4.
8. Vehicle speed is more than 5 MPH.
9. Transmission fluid temperature is 68-266°F (20-130°C).
10. Traction control is not active (if equipped).
11. All conditions have been met and any combination of the following conditions occur 2 consecutive times.

Condition No. 1

1. Commanded 1-2 shift.
2. Throttle angle is 17-42 percent.
3. Throttle angle stays constant within 3 percent.
4. Vehicle speed is 5-30 MPH.
5. Within 2.5 seconds, engine speed in 2nd gear must be 150 RPM more than last speed in 1st gear.

Condition No. 2

1. Commanded 2-3 shift.
2. Throttle angle is 17-32 percent.
3. Throttle angle stays constant within 5 percent.
4. Vehicle speed is 20-45 MPH.
5. Within 1.7 seconds, engine speed in 3rd gear must be 75 RPM less than last speed in 2st gear.

Condition No. 3

1. Commanded 3-4 shift.
2. Throttle angle is 17-30 percent.
3. Throttle angle stays constant within 3 percent.
4. Vehicle speed is 28-65 MPH.
5. Within 3 seconds, engine speed in 4th gear must be 20 RPM more than last speed in 3rd gear.

Condition No. 4

1. Commanded 4th gear.
2. TCC is on.
3. Throttle angle is 13-26 percent.
4. Speed ratio (engine speed divided by output speed) is .85-1.2.
5. TCC slip speed is 300-2000 RPM for more than 4 seconds.

Condition No. 5

1. Commanded 4th gear.
2. TCC is on.
3. Throttle angle is 13-26 percent.
4. Speed ratio (engine speed divided by output speed) is .5-.79.
5. TCC slip speed is between -20 and 20 RPM for more than 4 seconds.

DTC P0751 will be stored in PCM history. MIL will light at first failure signal, PCM freezes shift adapts from being updated and line pressure defaults to D2.

1. 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, go to next step. If gear position does not match transmission range switch on scan tool, diagnose Transmission Fluid Pressure (TFP) position switch. Switch is also referred to as Pressure Switch Assembly (PSA). See «COMPONENT TESTS»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e) .
3. Raise and support vehicle. Shift gear selector into D4 position. Using scan tool, command 1st, 2nd, 3rd and 4th gears while accelerating vehicle. If a 1-1-4-4 or 2-2-3-3 shift pattern is not detected, see DIAGNOSTIC AIDS below. If a 1-1-4-4 or 2-2-3-3 shift pattern is detected, check shift solenoids for damaged seals or internal malfunction. Repair shift solenoids as necessary, then go to next step.
4. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Test drive vehicle. Hold throttle at 20 percent and accelerate vehicle to 55 MPH. If throttle moves more than 3 percent, stop vehicle and start again. Drive vehicle at 55 MPH for 3 miles. Select "Specific DTC" and enter DTC "P0751". If DTC P0751 is not present, repair is complete. If DTC P0751 is still present, repeat test.

Verify shift speeds are correct. See AUTO TRANS OVERHAUL - 4L60-E article. More than one shift may occur due to other internal transmission failures.

P0753, 1-2 SHIFT SOLENOID ("A") ELECTRICAL MALFUNCTION

Note. Perform OBD system check prior to performing diagnostic procedures. For wire circuit identification, see WIRING DIAGRAMS .

The 1-2 shift solenoid (solenoid "A") is used to control fluid flow acting on 1-2 shift valve. Solenoid is a normally open exhaust valve that is used in conjunction with 2-3 shift solenoid (solenoid "B"), to allow 4 different shifting combinations. See the SHIFT SOLENOID COMBINATIONS table. Solenoid is attached to control valve body. Ignition voltage is supplied directly to solenoid through fused circuit. PCM commands solenoid on or off through ground circuit. DTC P0753 detects a continuous open or short to ground in 1-2 shift solenoid circuit.

Conditions For Setting DTC P0753

DTC will set under the following conditions

1. Ignition is on.
2. System voltage is 10-17 volts.
3. PCM commands solenoid on and voltage remains high (battery voltage).
4. PCM commands solenoid off and voltage remains low (zero volts).
5. All conditions are met for 5 seconds.

DTC P0753 will be stored in PCM history. MIL will light at first failure signal, PCM freezes shift adapts from being updated and defaults to maximum line pressure.

SHIFT SOLENOID COMBINATIONS

1. 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. If DTCs P0758, P1860, P1864 and P1886 are not present, go to next step. If DTCs P0753, P0758, P1860, P1864 and P1886 are present, remove appropriate 1-2 shift solenoid ignition feed circuit fuse from underhood electrical center and inspect fuse. Refer to the «WIRING DIAGRAMS»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e) . Replace fuse if necessary, and check for short to ground in wiring harness between transmission 20-pin connector and fuse. Repair wiring as necessary, then go to step 12. If fuse is okay, check for open in wiring harness between transmission 20-way connector and fuse. Repair wire as necessary, then go to step 12.
3. Using scan tool, command 1-2 shift solenoid on and off 3 times while listening at transmission oil pan. If solenoid does not click when commanded on and off, go to next step. If solenoid clicks when commanded on and off, inspect wiring for poor connections at PCM and transmission 20-pin connector. Check for possible bent, backed out, deformed or damaged terminals. Repair as necessary, then go to step 12. If connections and terminals are okay, see DIAGNOSTIC AIDS below.
4. Turn ignition off. Disconnect transmission 20-pin connector. Install Jumper Harness (J-39775) to PCM side of transmission 20-pin connector. Connect test light between ground and 1-2 shift solenoid ignition feed circuit at transmission 20-pin connector. Turn ignition switch to ON position. DO NOT start engine.
5. If test light does not light, check for open or short to ground in ignition feed circuit of 1-2 shift solenoid. Repair as necessary, then go to step 12. If test light lights, connect test light between 1-2 shift solenoid ground circuit and ignition feed circuit at transmission 20-pin connector. Using scan tool, command 1-2 shift solenoid on and off 3 times. If test light cycles on and off, go to step 8. If test light does not cycle on and off 3 times, and test light is always on, go to next step. If test light is always off, go to step 7.
6. Check 1-2 shift solenoid ground circuit for short to ground. Repair circuit as necessary, then go to step 12. If circuit is okay, inspect wiring for poor connections at PCM connector. Check for possible bent, backed out, deformed or damaged terminals. Repair as necessary, then go to step 12. If connections and terminals are okay, replace PCM, then go to step 12.
7. Check for open in 1-2 shift solenoid ignition feed circuit or poor connection at PCM connector. Repair circuit as necessary, then go to step 12. If circuit is okay, inspect wiring for poor connections at PCM connector. Check for possible bent, backed out, deformed or damaged terminals. Repair as necessary, then go to step 12. If connections and terminals are okay, replace PCM, then go to step 12.
8. Turn ignition off. Disconnect jumper harness from PCM side of transmission 20-pin connector and install harness to transmission side of 20-pin connector. Connect ohmmeter between 1-2 shift solenoid ground circuit and ignition feed circuit at transmission 20-pin connector.
9. If resistance is 19-31 ohms, go to next step. If resistance is not 19-31 ohms, disconnect 1-2 shift solenoid connector. Measure resistance between 1-2 shift solenoid terminals. If resistance is 19-31 ohms, check for open circuit in transmission wiring harness. Repair as necessary, then go to step 12. If resistance is not 19-31 ohms, replace 1-2 shift solenoid, then go to step 12.
10. Turn ignition off. Connect ohmmeter between ground and 1-2 shift solenoid ground circuit, and between ground and 1-2 shift solenoid ignition feed circuit at transmission 20-pin connector. If resistance is more 250 k/ohms, see DIAGNOSTIC AIDS below. If resistance is less than 250k/ohms, go to next step.
11. Disconnect 1-2 shift solenoid connector. Measure resistance between ground and each solenoid terminal. If resistance is more than 250 k/ohms, check for short to ground in transmission wiring harness. Repair as necessary, then go to next step. If resistance is less than 250 k/ohms, replace 1-2 shift solenoid, then go to next step.
12. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Test drive vehicle. Ensure voltage decreases to zero when1-2 shift solenoid is commanded on, and voltage increases to battery voltage when commanded off. Conditions must be met for 5 seconds. Select "Specific DTC" and enter DTC "P0753". If DTC P0753 is not present, repair is complete. If DTC P0753 is still present, repeat test.

Inspect wiring for poor connections at PCM. Check for possible bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wire that could short to bare metal or other wiring. Check for broken wire inside insulation. If diagnosing for possible intermittent short or open condition, move wiring harness while observing scan tool for value change.

P0756, 2-3 SHIFT SOLENOID ("B") PERFORMANCE MALFUNCTION

Note. Perform OBD system check prior to performing diagnostic procedures. For wire circuit identification, see WIRING DIAGRAMS.

The 2-3 shift solenoid (solenoid "B") is a normally open exhaust valve that is used in conjunction with 1-2 shift solenoid (solenoid "A"), to allow 4 different shifting combinations. Solenoid is attached to control valve body. DTC P0756 detects a 1-2-2-1 or a 4-3-3-4 shift pattern, depending on mechanical failure.

Conditions For Setting DTC P0756

DTC will set under the following conditions

1. DTCs P0122 or P0123 (throttle position) are not present.
2. DTC P0502 (vehicle speed sensor) is not present.
3. DTCs P0712 or P0713 (TFT sensor) are not present.
4. DTC P0742 (TCC stuck on) is not present.
5. DTCs P0753 and P0758 (1-2 and 2-3 shift solenoid electrical) are not present.
6. DTC P1810 (temperature fluid pressure position switch) is not present.
7. DTC P1860 (TCC PWM solenoid) is not present.
8. DTC P1864 (TCC solenoid) is not present.
9. DTC P1886 (3-2 shift solenoid) is not present.
10. Gear range is D4.
11. TCC is off.
12. Vehicle speed is more than 15 MPH.
13. Transmission fluid temperature is 68-266°F (20-130°C).
14. Engine speed is more than 450 RPM for 2 seconds and less than 5500 RPM.
15. All conditions are met and either one of the following fail conditions occurs
16. Solenoid is stuck on and Conditions No. 2 and 3 occur 2 consecutive times.
17. Solenoid is stuck off and Conditions No. 1 and 3 occur 2 consecutive times.

1. 1st gear is commanded for 2.5 seconds.
2. Throttle angle is more than 38 percent.
3. Speed ratio (engine speed divided by output speed) is .5-2.59.
4. TCC slip speed is between -93 and -2000 RPM for 1.6 seconds.
5. Transmission output speed is 600-1500 RPM.

1. 3rd gear is commanded for one second.
2. Throttle angle is 13-55 percent.
3. Throttle angle stays constant within 3 percent.
4. 3rd gear speed ratio is more than last 2nd gear speed ratio minus .2.
5. 3rd gear TCC slip speed is more than or equal to last 2nd gear TCC slip speed plus 200 RPM for 1.3 seconds.
6. Discontinue test if time since shift commanded is more than 5 seconds.

1. 4th gear is commanded for one second.
2. Throttle angle is more than 18 percent.
3. Speed ratio (engine speed divided by output speed) is 2.05-8.00.
4. TCC slip speed is 1000-4000 RPM for 3 seconds.
5. Transmission output speed is 0-8191 RPM.

DTC P0756 will be stored in PCM history. MIL will light at first failure signal, PCM freezes shift adapts from being updated and commands maximum line pressure.

1. 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, go to next step. If gear position does not match transmission range switch on scan tool, diagnose Transmission Fluid Pressure (TFP) position switch. Switch is also referred to as Pressure Switch Assembly (PSA). See «COMPONENT TESTS»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e) .
3. Raise and support vehicle. Shift gear selector into D4 position. Using scan tool, command 1st, 2nd, 3rd and 4th gears while accelerating vehicle. If 1st gear was commanded but not achieved or gear other than 4th gear occurred in 4th gear, check shift solenoids for damaged seals or internal malfunction. Repair shift solenoids as necessary, then go to next step. If all gears commanded were achieved, see DIAGNOSTIC AIDS below.
4. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Test drive vehicle. Hold throttle at 50 percent and accelerate vehicle to 55 MPH. If throttle moves more than 3 percent, stop vehicle and start again. Hold throttle at 20 percent and accelerate vehicle to 55 MPH. Select "Specific DTC" and enter DTC "P0756". If DTC P0756 is not present, repair is complete. If DTC P0756 is still present, repeat test.

Verify shift speeds are correct. See AUTO TRANS OVERHAUL - 4L60-E article. More than one shift may occur due to other internal transmission failures.

P0758, 2-3 SHIFT SOLENOID ("B") ELECTRICAL MALFUNCTION

Note. Perform OBD system check prior to performing diagnostic procedures. For wire circuit identification, see WIRING DIAGRAMS.

The 2-3 shift solenoid (solenoid "B") is used to control fluid flow acting on 2-3 shift valve. Solenoid is a normally open exhaust valve that is used in conjunction with 1-2 shift solenoid (solenoid "A"), to allow 4 different shifting combinations. See the SHIFT SOLENOID COMBINATIONS table. Solenoid is attached to control valve body. Ignition voltage is supplied directly to solenoid through fused circuit. PCM commands solenoid on or off through ground circuit. DTC P0758 detects a continuous open or short to ground in 2-3 shift solenoid circuit.

Conditions For Setting DTC P0758

DTC will set under the following conditions

1. Ignition is on.
2. System voltage is 10-17 volts.
3. PCM commands solenoid on and voltage remains high (battery voltage).
4. PCM commands solenoid off and voltage remains low (zero volts).
5. All conditions are met for 5 seconds.

DTC P0758 will be stored in PCM history. MIL will light at first failure signal, PCM inhibits TCC engagement, freezes shift adapts from being updated and commands maximum line pressure. Transmission operates in 3rd gear only.

SHIFT SOLENOID COMBINATIONS

1. 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. If DTCs P0753, P1860, P1864 and P1886 are not present, go to next step. If DTCs P0753, P0758, P1860, P1864 and P1886 are present, remove appropriate 2-3 shift solenoid ignition feed circuit fuse from underhood electrical center and inspect fuse. Refer to the «WIRING DIAGRAMS»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e) . Replace fuse if necessary, and check for short to ground in wiring harness between transmission 20-pin connector and fuse. Repair wiring as necessary, then go to step 12. If fuse is okay, check for open in wiring harness between transmission 20-way connector and fuse. Repair wire as necessary, then go to step 12.
3. Using scan tool, command 2-3 shift solenoid on and off 3 times while listening at transmission oil pan. If solenoid does not click when commanded on and off, go to next step. If solenoid clicks when commanded on and off, inspect wiring for poor connections at PCM and transmission 20-pin connector. Check for possible bent, backed out, deformed or damaged terminals. Repair as necessary, then go to step 12. If connections and terminals are okay, see DIAGNOSTIC AIDS below.
4. Turn ignition off. Disconnect transmission 20-pin connector. Install Jumper Harness (J-39775) to PCM side of transmission 20-pin connector. Connect test light between ground and 2-3 shift solenoid ignition feed circuit at transmission 20-pin connector. Turn ignition switch to ON position. DO NOT start engine.
5. If test light does not light, check for open or short to ground in ignition feed circuit of 2-3 shift solenoid. Repair as necessary, then go to step 12. If test light lights, connect test light between 2-3 shift solenoid ground circuit and ignition feed circuit at transmission 20-pin connector. Using scan tool, command 2-3 shift solenoid on and off 3 times. If test light cycles on and off, go to step 8. If test light does not cycle on and off 3 times, and test light is always on, go to next step. If test light is always off, go to step 7.
6. Check 2-3 shift solenoid ground circuit for short to ground. Repair circuit as necessary, then go to step 12. If circuit is okay, inspect wiring for poor connections at PCM connector. Check for possible bent, backed out, deformed or damaged terminals. Repair as necessary, then go to step 12. If connections and terminals are okay, replace PCM, then go to step 12.
7. Check for open in 2-3 shift solenoid ignition feed circuit or poor connection at PCM connector. Repair circuit as necessary, then go to step 12. If circuit is okay, inspect wiring for poor connections at PCM connector. Check for possible bent, backed out, deformed or damaged terminals. Repair as necessary, then go to step 12. If connections and terminals are okay, replace PCM, then go to step 12.
8. Turn ignition off. Disconnect jumper harness from PCM side of transmission 20-pin connector and install harness to transmission side of 20-pin connector. Connect ohmmeter between 2-3 shift solenoid ground circuit and ignition feed circuit at transmission 20-pin connector.
9. If resistance is 19-31 ohms, go to next step. If resistance is not 19-31 ohms, disconnect 2-3 shift solenoid connector. Measure resistance between 2-3 shift solenoid terminals. If resistance is 19-31 ohms, check for open circuit in transmission wiring harness. Repair as necessary, then go to step 12. If resistance is not 19-31 ohms, replace 2-3 shift solenoid, then go to step 12.
10. Turn ignition off. Connect ohmmeter between ground and 2-3 shift solenoid ground circuit, and between ground and 2-3 shift solenoid ignition feed circuit at transmission 20-pin connector. If resistance is more than 250 k/ohms, see DIAGNOSTIC AIDS below. If resistance is less than 250 k/ohms, go to next step.
11. Disconnect 2-3 shift solenoid connector. Measure resistance between ground and each solenoid terminal. If resistance is more than 250 k/ohms, check for short to ground in transmission wiring harness. Repair as necessary, then go to next step. If resistance is less than 250 k/ohms, replace 2-3 shift solenoid, then go to next step.
12. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Test drive vehicle. Ensure voltage decreases to zero when2-3 shift solenoid is commanded on, and voltage increases to battery voltage when commanded off. Conditions must be met for 5 seconds. Select "Specific DTC" and enter DTC "P0758". If DTC P0758 is not present, repair is complete. If DTC P0758 is still present, repeat test.

Inspect wiring for poor connections at PCM. Check for possible bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wire that could short to bare metal or other wiring. Check for broken wire inside insulation. If diagnosing for possible intermittent short or open condition, move wiring harness while observing scan tool for value change.

P1572, TRACTION CONTROL SYSTEM (TCS) LOW VOLTAGE TOO LONG

Note. Perform OBD system check prior to performing diagnostic procedures. For wire terminal locations, see WIRING DIAGRAMS .

PCM receives an input signal from Traction Control System (TCS) indicating a traction control event is occurring. Battery positive signal during normal operation becomes zero volts during traction control event. PCM inhibits upshifts, downshifts and TCC operation during event. DTC P1572 detects an active traction control circuit in Park and Neutral.

Conditions For Setting DTC P1572

DTC will set under the following conditions

1. DTC P1810 (TFP position switch) is not present.
2. Transmission is in Park or Neutral.
3. Traction control is active.
4. All conditions are met for 6.4 seconds.

DTC P1572 will be stored in PCM history. MIL will light at first failure signal. If TCS is active, TCC is off. PCM inhibits 4th gear if in hot mode and freezes shift adapts.

1. 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. If scan tool does not display traction control as "Active", see DIAGNOSTIC AIDS below. If scan tool displays traction control as "Active", turn ignition off. Disconnect appropriate PCM connector connected to traction control system. See «WIRING DIAGRAMS»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e) . Turn ignition switch to ON position. DO NOT start engine. If scan tool does not display traction control "Active", replace PCM, then go to next step. If scan tool displays traction control "Active", diagnose using appropriate Anti-lock Brake System (ABS) or Traction Control System (TCS) test information in ENGINE PERFORMANCE section.
3. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Ensure traction control is NOT active for 6.4 seconds. Select "Specific DTC" and enter DTC "P1572". If DTC P1572 is not present, repair is complete. If DTC P1572 is still present, repeat test.

Inspect wiring for poor connections at PCM and brake switch. Check for possible bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for broken wire inside insulation. If diagnosing for possible intermittent short or open condition, move wiring harness while observing scan tool for value change.

P1810, TRANSMISSION FLUID PRESSURE (TFP) POSITION SWITCH ASSEMBLY MALFUNCTION

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).

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 .

TFP LOGIC

Conditions For Setting DTC P1810

DTC will set when any one of the following 3 conditions occur

This condition detects an illegal switch combination.

1. System voltage is 10-17 volts
2. Engine is running.
3. PCM detects an illegal TFP state.
4. All conditions are met for 5 seconds.

This condition detects D2, D4 or Reverse during an engine start.

1. DTC P0502 (vehicle speed sensor) is not present.
2. 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.
3. Vehicle speed is less than 2 MPH.
4. Detected gear range is D2, D4 or Reverse.
5. All conditions are met for 3 seconds.

This condition detect Park or Neutral when vehicle should be in D4.

1. DTC P0502 (vehicle speed sensor) is not present.
2. Engine speed is less than 2000 RPM.
3. Speed ratio (engine speed divided by output speed) is .39-.80.
4. TCC is locked on.
5. Detected gear range is Park or Neutral.
6. 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.

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»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e) . 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 below. 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. Refer to the «WIRING DIAGRAMS»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e) . 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, then go 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»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e) .
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.

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.

P1812, TRANSMISSION FLUID OVERTEMP

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).

Transmission Fluid Temperature (TFT) sensor is a negative coefficient thermistor within Transmission Fluid Pressure (TFP) position switch. TFT sensor controls signal voltage to PCM. PCM provides a 5 volt reference to sensor on TFT signal circuit. When transmission fluid is cold, sensor resistance is high, and PCM detects high signal voltage. As transmission fluid temperature increases, sensor resistance decreases and voltage decreases. At normal operating temperature of 212°F (100°C), voltage is about 1.5-2 volts. DTC P1812 detects high transmission temperature for long periods of time.

Conditions For Setting DTC P1812

DTC will set under the following conditions

1. DTC P0712 or P0713 (TFT sensor) are not present.
2. Transmission fluid temperature is more than 266°F (130°C).
3. All conditions are met for 15 minutes.

DTC P1812 will be stored in PCM history. MIL will NOT light. PCM freezes shift adapts from being updated.

1. Check transmission fluid. Fill as needed. Check for possible engine cooling system problems. Repair as necessary.
2. 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.
3. Using scan tool, check TFT sensor signal voltage. If scan tool displays less than .33 volts, go to next step. If scan tool displays more than .33 volts, see DIAGNOSTIC AIDS below.
4. Turn ignition switch off. Disconnect transmission 20-pin connector. If scan tool displays more than 4.92 volts, perform COMPONENT & WIRING HARNESS RESISTANCE CHECK under «COMPONENT TESTS»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e) . If scan tool displays less than 4.92 volts, go to next step.
5. Check TFT sensor signal circuit for short to ground. Repair circuit as necessary, then go to next step. If circuit is okay, inspect wiring for poor connections at PCM connector. Check for possible bent, backed out, deformed or damaged terminals. Repair as necessary, then go to next step. If connections and terminals are okay, replace PCM, then go to next step.
6. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Select "Specific DTC" and enter DTC "P1812". Turn ignition switch to ON position. Scan tool must indicate fluid temperature less than 264°F (129°C) for at least 5 seconds. If DTC P1812 is not present, repair is complete. If DTC P1812 is still present, repeat test.

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. Check for torque converter stator malfunction.

P1860, TCC PWM SOLENOID ELECTRICAL MALFUNCTION

Note. Perform OBD system check prior to performing diagnostic procedures. For wire circuit identification, see WIRING DIAGRAMS .

TCC PWM solenoid is used to control fluid flow acting on converter clutch valve. Solenoid controls TCC apply and release. Solenoid is attached to control valve body. Ignition voltage is supplied directly to solenoid through fused circuit. PCM commands solenoid on or off through ground circuit. TCC PWM solenoid provides a smooth engagement of TCC by operating during duty cycle percent of on time. DTC P1860 detects a continuous open or short to ground in TCC PWM solenoid circuit.

Conditions For Setting DTC P1860

DTC will set under the following conditions

1. 1st gear is commanded.
2. Ignition is on.
3. DTC P0751 or P0753 (1-2 shift solenoid) are not present.
4. DTC P0756 or P0758 (2-3 shift solenoid) are not present.
5. System voltage is 10-17 volts.
6. TCC is at 100 percent duty cycle for more than .1 second.
7. TCC is at zero percent duty cycle for more than .5 seconds.
8. PCM commands solenoid off and voltage remains low (zero volts).
9. All conditions are met for 5 seconds.

DTC P1860 will be stored in PCM history. MIL will light at first failure signal, PCM inhibits TCC engagement, inhibits 4th gear if in hot mode, freezes shift adapts from being updated and commands maximum line pressure.

1. 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. If DTCs P0753, P0758, P1860, P1864 and P1886 are not present, go to next step. If DTCs P0753, P0758, P1860, P1864 and P1886 are present, remove appropriate TCC PWM solenoid ignition feed circuit fuse from underhood electrical center (cars) or from instrument panel fuse block (light trucks and vans) and inspect fuse. Refer to the «WIRING DIAGRAMS»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e) . Replace fuse if necessary, and check for short to ground in wiring harness between transmission 20-pin connector and fuse. Repair wiring as necessary, then go to step 10. If fuse is okay, check for open in wiring harness between transmission 20-way connector and fuse. Repair wire as necessary, then go to step 10.
3. Turn ignition off. Disconnect transmission 20-pin connector. Install Jumper Harness (J-39775) to PCM side of transmission 20-pin connector. Connect test light between ground and TCC PWM solenoid ignition feed circuit at transmission 20-pin connector. Turn ignition switch to ON position. DO NOT start engine.
4. If test light does not light, check for open or short to ground in ignition feed circuit of TCC PWM solenoid. Repair as necessary, then go to step 10. If test light lights, connect test light between TCC PWM solenoid ground circuit and ignition feed circuit at transmission 20-pin connector. Using scan tool, command TCC PWM solenoid on and off 3 times.
5. If test light cycles on and off, go to next step. If test light does not cycle on and off 3 times, check TCC PWM solenoid ground circuit for open or short to ground. Repair circuit as necessary, then go to step 10. If circuit is okay, inspect wiring for poor connections at PCM connector. Check for possible bent, backed out, deformed or damaged terminals. Repair as necessary, then go to step 10. If connections and terminals are okay, replace PCM, then go to step 10.
6. Turn ignition off. Disconnect jumper harness from PCM side of transmission 20-pin connector and install harness to transmission side of 20-pin connector. Connect ohmmeter between TCC PWM solenoid ground circuit and ignition feed circuit at transmission 20-pin connector.
7. If resistance is 10-15 ohms, go to next step. If resistance is not 10-15 ohms, disconnect TCC PWM solenoid connector. Measure resistance between TCC PWM solenoid terminals. If resistance is 10-15 ohms, check for open circuit in transmission wiring harness. Repair as necessary, then go to step 10. If resistance is not 10-15 ohms, replace TCC PWM solenoid, then go to step 10.
8. Turn ignition off. Connect ohmmeter between ground and TCC PWM solenoid ground circuit, and between ground and TCC PWM solenoid ignition feed circuit at transmission 20-pin connector. If resistance is more than 250 k/ohms, see DIAGNOSTIC AIDS below. If resistance is less than 250 k/ohms, go to next step.
9. Disconnect TCC PWM solenoid connector. Measure resistance between ground and each solenoid terminal. If resistance is more than 250 k/ohms, check for short to ground in transmission wiring harness. Repair as necessary, then go to next step. If resistance is less than 250 k/ohms, replace TCC PWM solenoid, then go to next step.
10. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Test drive vehicle. Ensure voltage decreases to zero when TCC PWM solenoid is commanded on, and voltage increases to battery voltage when commanded off. Conditions must be met for 5 seconds. Select "Specific DTC" and enter DTC "P1860". If DTC P1860 is not present, repair is complete. If DTC P1860 is still present, repeat test.

Inspect wiring for poor connections at PCM and transmission 20-pin connector. Check for possible bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wire that could short to bare metal or other wiring. Check for broken wire inside insulation. If diagnosing for possible intermittent short or open condition, move wiring harness while observing scan tool for value change.

P1864, TCC SOLENOID ELECTRICAL MALFUNCTION

Note. Perform OBD system check prior to performing diagnostic procedures. For wire circuit identification, see WIRING DIAGRAMS .

In conjunction with TCC PWM solenoid, TCC solenoid is used to control fluid flow acting on TCC valve. TCC valve controls apply and release of TCC. Solenoid is a normally-open on/off device. Solenoid is attached to transmission case and extends into oil pump cover. PCM monitors TP voltage, vehicle speed and other input devices in order to determine when to energize TCC solenoid. Ignition voltage is supplied directly to solenoid through fused circuit. PCM commands solenoid on or off through ground circuit. DTC P1864 detects a continuous open or short to ground in TCC solenoid circuit.

Conditions For Setting DTC P1864

DTC will set under the following conditions

1. Ignition is on.
2. System voltage is 10-17 volts.
3. PCM commands solenoid on and voltage remains high (battery voltage).
4. PCM commands solenoid off and voltage remains low (zero volts).
5. All conditions are met for 5 seconds.

DTC P1864 will be stored in PCM history. MIL will light at first failure signal, PCM inhibits TCC engagement, inhibits 4th gear if in hot mode and freezes shift adapts from being updated.

1. 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. If DTCs P0753, P0758, P1860, P1864 and P1886 are not present, go to next step. If DTCs P0753, P0758, P1860, P1864 and P1886 are present, remove appropriate TCC solenoid ignition feed circuit fuse from underhood electrical center (cars) or from instrument panel fuse block (light trucks and vans) and inspect fuse. Refer to the «WIRING DIAGRAMS»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e) . Replace fuse if necessary, and check for short to ground in wiring harness between transmission 20-pin connector and fuse. Repair wiring as necessary, then go to step 10. If fuse is okay, check for open in wiring harness between transmission 20-way connector and fuse. Repair wire as necessary, then go to step 10.
3. Turn ignition off. Disconnect transmission 20-pin connector. Install Jumper Harness (J-39775) to PCM side of transmission 20-pin connector. Connect test light between ground and TCC solenoid ignition feed circuit at transmission 20-pin connector. Turn ignition switch to ON position. DO NOT start engine.
4. If test light does not light, check for open or short to ground in ignition feed circuit of TCC solenoid. Repair as necessary, then go to step 10. If test light lights, connect test light between TCC solenoid ground circuit and ignition feed circuit at transmission 20-pin connector. Using scan tool, command TCC solenoid on and off 3 times.
5. If test light cycles on and off, go to next step. If test light does not cycle on and off 3 times, check TCC solenoid ground circuit for open or short to ground. Repair circuit as necessary, then go to step 10. If circuit is okay, inspect wiring for poor connections at PCM connector. Check for possible bent, backed out, deformed or damaged terminals. Repair as necessary, then go to step 10. If connections and terminals are okay, replace PCM, then go to step 10.
6. Turn ignition off. Disconnect jumper harness from PCM side of transmission 20-pin connector and install harness to transmission side of 20-pin connector. Connect ohmmeter between TCC solenoid ground circuit and ignition feed circuit at transmission 20-pin connector.
7. If resistance is 21-33 ohms, go to next step. If resistance is not 21-33 ohms, disconnect TCC solenoid connector. Measure resistance between TCC solenoid terminals. If resistance is 21-33 ohms, check for open circuit in transmission wiring harness. Repair as necessary, then go to step 10. If resistance is not 21-33 ohms, replace TCC solenoid, then go to step 10.
8. Turn ignition off. Connect ohmmeter between ground and TCC solenoid ground circuit, and between ground and TCC solenoid ignition feed circuit at transmission 20-pin connector. If resistance is more than 250 k/ohms, see DIAGNOSTIC AIDS below. If resistance is less than 250k/ohms, go to next step.
9. Disconnect TCC solenoid connector. Measure resistance between ground and each solenoid terminal. If resistance is more than 250k/ohms, check for short to ground in transmission wiring harness. Repair as necessary, then go to next step. If resistance is less than 250 k/ohms, replace TCC solenoid, then go to next step.
10. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Test drive vehicle. Ensure voltage decreases to zero when TCC solenoid is commanded on, and voltage increases to battery voltage when commanded off. Conditions must be met for 5 seconds. Select "Specific DTC" and enter DTC "P1864". If DTC P1864 is not present, repair is complete. If DTC P1864 is still present, repeat test.

Inspect wiring for poor connections at PCM and transmission 20-pin connector. Check for possible bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wire that could short to bare metal or other wiring. Check for broken wire inside insulation. If diagnosing for possible intermittent short or open condition, move wiring harness while observing scan tool for value change.

P1870, TRANSMISSION COMPONENT SLIPPING

Note. Perform OBD system check prior to performing diagnostic procedures. For wire circuit identification, see WIRING DIAGRAMS .

PCM monitors difference between engine speed and transmission output speed. In D3 with TCC engaged, engine speed should closely match transmission output speed. In D4 with TCC engaged, TCC slip speed should be -20 to 20 RPM. DTC P1870 detects excessive TCC slip when TCC should be engaged.

Conditions For Setting DTC P1870

DTC will set under the following conditions

1. DTCs P0122 or P0123 (throttle position sensor) are not present.
2. DTCs P0172 or P0173 (TFT sensor) or DTC P0502 (vehicle speed sensor) are not present.
3. DTCs P0751 or P0753 (1-2 shift solenoid) are not present.
4. DTCs P0756 or P0758 (2-3 shift solenoid) are not present.
5. DTC P1810 (TFP position switch) is not present.
6. DTC P1860 (TCC PWM solenoid) is not present.
7. DTC P1864 (TCC solenoid) is not present.
8. Engine speed is less than 5500 RPM.
9. Gear range is D4.
10. Vehicle is not in 1st gear.
11. Throttle angle is 13-36 percent.
12. Transmission fluid temperature is 68-266°F (20-130°C).
13. TCC is on for more than 0.1 second.
14. TCC is at maximum apply for 0.1 second.
15. Shift solenoid performance counter is at zero.
16. TCC slip speed is more than 130 RPM for more than 8 seconds.

DTC P1870 will be stored in PCM history. MIL will light at first failure signal, PCM inhibits TCC engagement, inhibits 4th gear if in hot mode, freezes shift adapts from being updated and commands maximum line pressure.

1. 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, go to next step. If gear position does not match transmission range switch on scan tool, diagnose Transmission Fluid Pressure (TFP) position switch. Switch is also referred to as Pressure Switch Assembly (PSA). See «COMPONENT TESTS»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e) .
3. Drive vehicle in 4th gear while TCC is engaged. If TCC slip speed is more than 130 RPM for 10 seconds, go to TROUBLE SHOOTING in the AUTO TRANS OVERHAUL - 4L60-E article. If TCC slip speed is less than 130 RPM for 10 seconds, see DIAGNOSTIC AIDS below.

A TFP position switch (Pressure Switch Assembly) malfunction could set DTC P1870. Ensure final drive ratio matches PCM calibration. The following mechanical conditions could set DTC P1870

1. Shift solenoids.
2. TCC solenoid.
3. TCC PWM solenoid.
4. Internal transmission failures.
5. Engine misfire.
6. A transmission range switch DTC.

P1873, TORQUE CONVERTER STATOR TEMPERATURE SWITCH CIRCUIT LOW

Note. Perform OBD system check prior to performing diagnostic procedures. For wire circuit identification, see WIRING DIAGRAMS .

Torque converter stator temperature switch is a normally-open temperature sensitive switch which sends a signal to PCM. Signal begins action to cool torque converter. At transmission fluid temperatures of 327°F (164°C) or higher, switch closes and signal to PCM changes to zero volts. Switch grounds through transmission fluid cooler pipes. DTC P1873 detects that torque converter stator switch indicates a hot mode at low transmission temperature.

Conditions For Setting DTC P1873

DTC will set under the following conditions

1. DTCs P0712 or P0713 (TFT sensor) are not present.
2. Transmission fluid temperature is less than 104°F (60°C).
3. Torque converter stator temperature switch circuit indicates hot mode.
4. All conditions are met for 5 seconds.

DTC P1873 will be stored in PCM history. MIL will NOT light. Torque converter stator temperature switch does not indicate a hot mode. PCM freezes shift adapts from being updated.

1. Ensure transmission fluid level is correct. 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. Disconnect torque converter stator temperature switch connector. Using a grounded test light, probe torque converter stator temperature switch connector. Observe scan tool while connecting and disconnecting test light to switch connector.
3. If scan tool displays "TCC Stator Temp." as "High" (closed switch) with test light connected and "Normal" (open switch) with test light disconnected, replace torque converter stator temperature switch, then go to step 5. If scan tool does not display "TCC Stator Temp," as "High" with test light connected and "Normal" with test light disconnected, go to next step.
4. If scan tool displays "TCC Stator Temp." as "High" at all times, repair short to ground in switch input circuit, then go to next step. If scan tool does not display "TCC Stator Temp." as "High" at all times, see DIAGNOSTIC AIDS below.
5. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Ensure torque converter stator temperature switch circuit does not indicate a hot mode when transmission fluid temperature is less than 140°F (60°C). Select "Specific DTC" and enter DTC "P1873". If DTC P1873 is not present, repair is complete. If DTC P1873 is still present, repeat test.

If switch and external wiring are okay, verify circuit ground through transmission fluid cooler pipes. Inspect wiring for poor connections at PCM and transmission 20-pin connector. Check for possible bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wire that could short to bare metal or other wiring. Check for broken wire inside insulation. If diagnosing for possible intermittent short or open condition, move wiring harness while observing scan tool for value change.

P1874, TORQUE CONVERTER STATOR TEMPERATURE SWITCH CIRCUIT HIGH

Note. Perform OBD system check prior to performing diagnostic procedures. For wire circuit identification, see WIRING DIAGRAMS .

Torque converter stator temperature switch is a normally-open temperature sensitive switch which sends a signal to PCM. Signal begins action to cool torque converter. At transmission temperatures of 327°F (164°C) or higher, switch closes and signal to PCM changes to zero volts. Switch grounds through transmission fluid cooler pipes. DTC P1874 detects that torque converter stator switch does not indicate a hot mode at high transmission temperature.

Conditions For Setting DTC P1874

DTC will set under the following conditions

1. DTCs P0712 or P0713 (TFT sensor) are not present.
2. Transmission fluid temperature is less than 284°F (140°C).
3. Torque converter stator temperature switch circuit does not indicate hot mode.
4. All conditions are met for 15 seconds.

DTC P1874 will be stored in PCM history. MIL will NOT light. Torque converter stator temperature switch indicates a hot mode. PCM freezes shift adapts from being updated.

1. Ensure transmission fluid level is correct. 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. Disconnect torque converter stator temperature switch connector. Using a grounded test light, probe torque converter stator temperature switch connector. Observe scan tool while connecting and disconnecting test light to switch connector.
3. If scan tool displays "TCC Stator Temp." as "High" (closed switch) with test light connected and "Normal" (open switch) with test light disconnected, replace torque converter stator temperature switch, then go to step 5. If scan tool does not display "TCC Stator Temp." as "High" with test light connected and "Normal" with test light disconnected, go to next step.
4. If scan tool displays "TCC Stator Temp." as "Normal" at all times, check for open or short to battery voltage in switch input circuit, then go to next step. If scan tool does not display "TCC Stator Temp." as "Normal" at all times, see DIAGNOSTIC AIDS below.
5. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Ensure torque converter stator temperature switch circuit indicates a hot mode when transmission fluid temperature is more than 284°F (140°C) for at least 15 seconds. Select "Specific DTC" and enter DTC "P1874". If DTC P1874 is not present, repair is complete. If DTC P1874 is still present, repeat test.

If switch and external wiring are okay, verify circuit ground through transmission fluid cooler pipes. Inspect wiring for poor connections at PCM and transmission 20-pin connector. Check for possible bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wire that could short to bare metal or other wiring. Check for broken wire inside insulation. If diagnosing for possible intermittent short or open condition, move wiring harness while observing scan tool for value change.

P1886, 3-2 SHIFT SOLENOID ELECTRICAL MALFUNCTION

Note. Perform OBD system check prior to performing diagnostic procedures. For wire circuit identification, see WIRING DIAGRAMS .

The 3-2 shift solenoid is a normally-closed 3-port on/off device which controls 3-2 downshift. Ignition voltage is supplied directly to solenoid through fused circuit. PCM commands solenoid on or off through ground circuit. During 3-2 downshift, 2-4 band applies as 3-4 clutch releases. PCM varies timing between 3-4 clutch release and 2-4 band apply depending on vehicle speed and throttle position. DTC P1886 detects a continuous open or short to ground in 3-2 shift solenoid circuit.

Conditions For Setting DTC P1886

DTC will set under the following conditions

1. System voltage is 10-17 volts.
2. Ignition is on.
3. PCM commands solenoid on and voltage remains high (battery voltage).
4. PCM commands solenoid off and voltage remains low (zero voltage).
5. All conditions are met for 5 seconds.

DTC P1886 will be stored in PCM history. MIL will light at first failure signal, PCM inhibits TCC engagement, inhibits 4th gear if in hot mode, freezes shift adapts from being updated and commands maximum line pressure. PCM commands a soft landing to 3rd gear.

1. 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. If DTCs P0753, P0758, P1860, P1864 and P1886 are not present, go to next step. If DTCs P0753, P0758, P1860, P1864 and P1886 are present, remove appropriate 3-2 shift solenoid ignition feed circuit fuse from underhood electrical center (cars) or from instrument panel fuse block (light trucks and vans) and inspect fuse. See «WIRING DIAGRAMS»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e) . Replace fuse if necessary, and check for short to ground in wiring harness between transmission 20-pin connector and fuse. Repair wiring as necessary, then go to step 10. If fuse is okay, check for open in wiring harness between transmission 20-way connector and fuse. Repair wire as necessary, then go to step 10.
3. Using scan tool, command 3-2 shift solenoid on and off 3 times while listening at transmission oil pan. If solenoid cycles, see DIAGNOSTIC AIDS below. If solenoid does not cycle, turn ignition off. Disconnect transmission 20-pin connector. Install Jumper Harness (J-39775) to PCM side of transmission 20-pin connector. Connect test light between ground and 3-2 shift solenoid ignition feed circuit at transmission 20-pin connector. Turn ignition switch to ON position. DO NOT start engine.
4. If test light does not light, check for open or short to ground in ignition feed circuit of 3-2 shift solenoid. Repair as necessary, then go to step 10. If test light lights, connect test light between 3-2 shift solenoid ground circuit and ignition feed circuit at transmission 20-pin connector. Using scan tool, command 3-2 shift solenoid on and off 3 times.
5. If test light cycles on and off, go to next step. If test light does not cycle on and off 3 times, check 3-2 shift solenoid ground circuit for open or short to ground. Repair circuit as necessary, then go to step 10. If circuit is okay, inspect wiring for poor connections at PCM connector. Check for possible bent, backed out, deformed or damaged terminals. Repair as necessary, then go to step 10. If connections and terminals are okay, replace PCM, then go to step 10.
6. Turn ignition off. Disconnect jumper harness from PCM side of transmission 20-pin connector and install harness to transmission side of 20-pin connector. Connect ohmmeter between 3-2 shift solenoid ground circuit and ignition feed circuit at transmission 20-pin connector.
7. If resistance is 20-32 ohms, go to next step. If resistance is not 20-32 ohms, disconnect 3-2 shift solenoid connector. Measure resistance between 3-2 shift solenoid terminals. If resistance is 20-32 ohms, check for open circuit in transmission wiring harness. Repair as necessary, then go to step 10. If resistance is not 20-32 ohms, replace 3-2 shift solenoid, then go to step 10.
8. Turn ignition off. Connect ohmmeter between ground and 3-2 shift solenoid ground circuit, and between ground and 3-2 shift solenoid ignition feed circuit at transmission 20-pin connector. If resistance is more than 250 k/ohms, see DIAGNOSTIC AIDS below. If resistance is less than 250 k/ohms, go to next step.
9. Disconnect 3-2 shift solenoid connector. Measure resistance between ground and each solenoid terminal. If resistance is more than 250k/ohms, check for short to ground in transmission wiring harness. Repair as necessary, then go to next step. If resistance is less than 250 k/ohms, replace 3-2 shift solenoid, then go to next step.
10. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Test drive vehicle. Ensure voltage decreases to zero when 3-2 shift solenoid is commanded on, and voltage increases to battery voltage when commanded off. Conditions must be met for 5 seconds. Select "Specific DTC" and enter DTC "P1886". If DTC P1886 is not present, repair is complete. If DTC P1886 is still present, repeat test.

Inspect wiring for poor connections at PCM and transmission 20-pin connector. Check for possible bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wire that could short to bare metal or other wiring. Check for broken wire inside insulation. If diagnosing for possible intermittent short or open condition, move wiring harness while observing scan tool for value change.

Note. Not all DTCs are applicable to all models.

Following diagnostic tests are DTC specific. Always perform On-Board Diagnostic (OBD) System Check prior to performing any diagnostic procedure. For terminal locations, see WIRING DIAGRAMS . For engine-related DTCs, see appropriate TESTS W/CODES article in ENGINE PERFORMANCE section.

Diagnostic aids located at end of each diagnostic test, are additional tips used to help diagnose trouble codes when diagnostic procedures do not find a problem.

PCM/VCM connector colors and terminal identification may vary with vehicle model and engine size. When using following diagnostic tests, see appropriate wiring diagram to determine which PCM/VCM connector(s) to disconnect during test procedure. Locate component being tested and trace specified wiring circuit to determine PCM/VCM connector and terminal related to that component.

Note. Vehicles equipped with a 2.2L engine are also equipped with a Powertrain Control Module (PCM). All other vehicles are equipped with a Vehicle Control Module (VCM).

Note. If a specific DTC diagnostic test is not included in the Light Trucks and Vans diagnostic tests, refer to the DIAGNOSTIC TESTS - PASSENGER CARS for the specific DTC. Test procedures not included for Light Trucks and Vans are the same as passenger car test procedures.

Note. Use of Tech 1 scan tool is required to perform OBD system check. Perform this test prior to performing any diagnostic procedures in DTC tests.

The OBD System Check determines

1. If Malfunction Indicator Light (MIL) works.
2. If PCM/VCM is operating and can recognize a fault.
3. If any codes are stored.

OBD system check is the starting point for utilizing the self-diagnostic system for determining computer-related problems. After performing necessary tests as described in diagnostic system check, if no codes are indicated and driveability problems still exist, see appropriate TESTS W/O CODES article in ENGINE PERFORMANCE section.

Note. The following steps should be performed first to reduce diagnostic time and prevent replacement of good parts.

2.2L

1. Turn ignition on, with engine off. Observe Malfunction Indicator Light (MIL). If MIL lights, go to next step. If MIL does not light, see A-1, MIL INOPERATIVE under appropriate BASIC TESTING article in ENGINE PERFORMANCE section.
2. Turn ignition off. Install scan tool and follow scan tool manufacturer's instructions to proceed with test. Turn ignition on. If scan tool displays PCM data, go to next step. If scan tool does not display PCM data, see A-4, NO SCAN TOOL DATA under appropriate BASIC TESTING article in ENGINE PERFORMANCE section.
3. Using scan tool, command MIL off. If MIL remains on, see A-2, MIL INOPERATIVE under appropriate BASIC TESTING article in ENGINE PERFORMANCE section. If MIL is off, using scan tool, check for any DTCs stored in LST TEST FAIL, FAIL THIS IGN., HISTORY or MIL REQUEST. If any DTC is stored, go to next step. If no DTCs are stored, go to step 5.
4. Using scan tool, save freeze frame and failure record information using "CAPTURE INFO" feature. If any DTC is indicated as last test failed, diagnose DTC. If DTC is not stored, check related circuit or component(s). See appropriate SYSTEM/COMPONENT TESTS article in ENGINE PERFORMANCE section.
5. Attempt to start engine. If engine starts and runs, go to next step. If engine does not start or starts and dies, see NO START DIAGNOSIS(A-3) under appropriate BASIC TESTING article in ENGINE PERFORMANCE section.
6. Turn ignition on, with engine off. Using scan tool, follow scan tool manufacturer's instructions to proceed with test. Check coolant temperature sensor and throttle position sensor operation. Start engine. Allow engine to reach normal operating temperature. Check coolant temperature, oxygen and manifold absolute pressure sensors and idle air control valve values.
7. Repair related circuit or component(s) as necessary. See appropriate SYSTEM/COMPONENT TESTS article in ENGINE PERFORMANCE section. If all components are okay, see appropriate TESTS W/O CODES article in the ENGINE PERFORMANCE section.

4.3L

1. Turn ignition off for 15 seconds. Turn ignition on. If MIL is on, go to next step. If MIL is off, see A-1, MIL INOPERATIVE under appropriate BASIC TESTING article in ENGINE PERFORMANCE section.
2. Install scan tool and follow scan tool manufacturer's instructions to proceed with test. Turn ignition on. If scan tool displays VCM data, go to next step. If scan tool does not display VCM data, go to NO SCAN TOOL DATA under appropriate BASIC TESTING article in ENGINE PERFORMANCE section.
3. Using scan tool, command MIL off. If MIL remains on, see A-2, MIL INOPERATIVE under appropriate BASIC TESTING article in ENGINE PERFORMANCE section. If MIL is off, using scan tool, check for any DTCs stored in LST TEST FAIL, FAIL THIS IGN., HISTORY or MIL REQUEST. If any DTC is stored, go to appropriate diagnostic test. If no DTCs are stored, go to next step.
4. Attempt to start engine. If engine starts and runs, go to next step. If engine does not start or starts and dies, go to ENGINE CRANKS BUT DOES NOT RUN under appropriate BASIC TESTING article in ENGINE PERFORMANCE section.
5. If DTCs are not present, compare scan tool data with specific component values. If values are not within specified range, check related circuit or component(s). See appropriate SYSTEM/COMPONENT TESTS article in ENGINE PERFORMANCE section.

5.0L & 5.7L

1. Turn ignition off. Connect scan tool and follow scan tool manufacturer's instructions to proceed with test. Turn ignition on. If MIL is on, go to next step. If MIL is off, see A-1, MIL INOPERATIVE under appropriate BASIC TESTING article in ENGINE PERFORMANCE section.
2. Turn ignition on, with engine off. If scan tool displays VCM data, go to next step. If scan tool does not display VCM data, go to NO SCAN TOOL DATA under appropriate BASIC TESTING article in ENGINE PERFORMANCE section.
3. Using scan tool, check for any DTCs stored in LST TEST FAIL, FAIL THIS IGN., HISTORY or MIL REQUEST. If any DTC's are stored, using scan tool, save freeze frame and failure record information using "CAPTURE INFO" feature, then diagnose DTC. If DTC is not stored, go to next step.
4. Attempt to start engine. If engine starts and runs, go to next step. If engine does not start or starts and dies, go to NO START DIAGNOSIS (A-3) under appropriate BASIC TESTING article in ENGINE PERFORMANCE section.
5. Compare scan tool data with specific component values. If values are not within specified range, check related circuit or component(s). See appropriate SYSTEM/COMPONENT TESTS article in ENGINE PERFORMANCE section.

P0502, VEHICLES SPEED SENSOR CIRCUIT (LOW INPUT)

Note. Perform OBD system check prior to performing diagnostic procedures. For wire circuit identification, see WIRING DIAGRAMS.

Vehicle speed is signaled to VCM by Vehicle Speed Sensor (VSS). Sensor is a Permanent Magnet (PM) generator mounted to transmission case extension. PM generator produces an AC voltage as speed sensor rotor teeth pass sensor's magnetic field. VCM converts AC voltage into digital signal. VCM uses vehicle speed to determine shift timing and TCC apply and release. VSS resistance value is 1480-2700 ohms. DTC P0502 detects a low vehicle output speed when vehicle has high engine speed in drive gear.

DTC will set under the following conditions

1. Transmission is not in Park or Neutral.
2. DTCs P0107 and P0108 (MAP sensor), or P0122 and P0123 (throttle position) are not present.
3. DTC P1810 (trans. fluid pressure position switch) is not present.
4. Engine speed more than 3000 RPM.
5. Throttle angle is more than 20 percent.
6. Output speed is less than 150 RPM.
7. All conditions are met for 3 seconds.

DTC P0502 will be stored in VCM history. MIL will light at first failure signal. VCM commands 2nd gear only, inhibits TCC solenoid engagement, freezes shift adapts from being updated and commands maximum line pressure.

1. 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. Raise and support vehicle.
2. Raise and support vehicle. Start engine and let idle. Apply brake pedal. Shift gear selector to any forward gear position. Select "Output Speed" on scan tool. With drive wheels rotating, if transmission output speed does not increase when wheel speed increases, go to next step. If transmission output speed increases when wheel speed increases, see DIAGNOSTIC AIDS below.
3. Ensure speedometer is operating. If speedometer is not operating, go to next step. If speedometer is operating, check for most current calibration. If calibration is current, check VCM connector for damaged or backed out connector terminals, weak terminal tension and poor connections. Repair as necessary, then go to step 8. If terminals and connections are okay, replace VCM, then go to step 8. If calibration is not current, reprogram VCM, then go to step 8. See «EEPROM REPROGRAMMING»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e__eeprom-reprogramming) procedure.
4. Turn ignition off. Disconnect appropriate VCM connector connected to VSS. See «WIRING DIAGRAMS»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e) . Using an ohmmeter, measure resistance between VSS terminals at appropriate VCM connector. If resistance is 1480-2700 ohms, go to next step. If resistance is not 1480-2700 ohms, check for poor connection or open circuit in VSS wiring. Repair as necessary, then go to step 8. If wiring is okay, go to step 7.
5. Shift transmission into Neutral. Connect DVOM between VSS terminals at appropriate VCM connector. See «WIRING DIAGRAMS»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e) . Rotate drive wheels and observe voltmeter display. If voltage is less than .5 volts, go to step 7. If voltage is more than .5 volts, reconnect appropriate VCM connector. Disconnect VSS connector. Turn ignition switch to ON position. Using DVOM, measure voltage between VSS connector terminals.
6. If voltage is 4.0-5.1 volts, check VCM connector for damaged or backed out connector terminals, weak terminal tension and poor connections. Repair as necessary, then go to step 8. If terminals and connections are okay, replace VCM, then go to step 8. If voltage is less than 4.0 volts, check VCM connector for damaged or backed out connector terminals, weak terminal tension and poor connections. Repair as necessary, then go to step 8. If terminals and connections are okay, replace VCM, then go to step 8. If voltage is more than 5.1 volts, repair short to voltage in output speed signal circuit, then go to step 8.
7. Remove VSS assembly. Check output shaft speed sensor rotor for damage or misalignment. Repair as necessary, then go to next step. If sensor rotor is okay, replace VSS assembly, then go to next step.
8. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Select "Specific DTC" and enter DTC "P0502". Test drive vehicle. Ensure transmission output speed is more than 151 RPM for 3 seconds. If DTC P0502 is not present, repair is complete. If DTC P0502 is still present, repeat test.

DTC P0502 sets when no vehicle speed is detected at start-off. Check for Electromagnetic Interferences (EMI) induced on VSS circuits. Check VCM connector and transmission 20-pin connector for bent, backed out or broken terminals or misaligned connectors. Inspect for damaged VSS or for damaged output speed sensor rotor teeth. Ensure VSS is aligned correctly and secured to transmission case properly. An incorrect calibration may set DTC P0502. If diagnosing for possible short or open condition, move wiring harness while observing scan tool for value changes.

EEPROM REPROGRAMMING

Note. Ignition switch should always be off when removing or installing VCM connectors.

Perform the following steps in order to set up EEPROM PROGRAMMING.

1. Ensure battery is fully charged.
2. Turn ignition switch to ON position.
3. Ensure battery and cigarette lighter connection is secure.
4. Connect scan tool to DLC. Refer to scan tool manufacturer's instructions to precede with reprogramming. If VCM fails to reprogram, check all VCM connections for proper connection. Check scan tool equipment for latest software version. Retry reprogramming steps. If VCM will not reprogram, replace VCM. Using scan tool, perform IAC valve reset procedure. For a functional check, perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK.

Note. Perform OBD system check prior to performing diagnostic procedures. For wire circuit identification, see WIRING DIAGRAMS .

The 1-2 shift solenoid (solenoid "A") is used to control fluid flow acting on 1-2 shift valve. Solenoid is a normally open exhaust that is used in conjunction with the 2-3 shift solenoid (solenoid "B"), to allow 4 different shifting combinations. Refer to the SHIFT SOLENOID COMBINATIONS table. Solenoid is attached to control valve body. Ignition voltage is supplied directly to solenoid through fused circuit. VCM commands solenoid on or off through ground circuit. DTC P0753 detects a continuous open or short to ground in 1-2 shift solenoid circuit.

DTC will set under the following conditions

1. Ignition is on.
2. System voltage is 10-17 volts.
3. VCM commands solenoid on and voltage remains high (battery voltage).
4. VCM commands solenoid off and voltage remains low (zero volts).
5. All conditions are met for 5 seconds.

DTC P0753 will be stored in VCM history. MIL will light at first failure signal, VCM freezes shift adapts from being updated and defaults to maximum line pressure.

SHIFT SOLENOID COMBINATIONS

1. 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. If DTCs P0758, P1860, P1864 and P1886 are not present, go to next step. If DTCs P0753, P0758, P1860, P1864 and P1886 are present, remove TRANS fuse from instrument panel fuse block and inspect fuse. See «WIRING DIAGRAMS»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e) . Replace fuse if necessary, and check for short to ground in wiring harness between transmission 20-pin connector and fuse. Repair wiring as necessary, then go to step 12. If fuse is okay, check for open in wiring harness between transmission 20-way connector and fuse. Repair wire as necessary, then go to step 12.
3. Using scan tool, command 1-2 shift solenoid on and off 3 times while listening at transmission oil pan. If solenoid does not click when commanded on and off, go to next step. If solenoid clicks when commanded on and off, inspect wiring for poor connections at VCM and transmission 20-pin connector. Check for possible bent, backed out, deformed or damaged terminals. Repair as necessary, then go to step 12. If connections and terminals are okay, see DIAGNOSTIC AIDS below.
4. Turn ignition off. Disconnect transmission 20-pin connector. Install Jumper Harness (J-39775) to VCM side of transmission 20-pin connector. Connect test light between ground and 1-2 shift solenoid ignition feed circuit at transmission 20-pin connector. Turn ignition switch to ON position. DO NOT start engine.
5. If test light does not light, check for open or short to ground in ignition feed circuit of 1-2 shift solenoid. Repair as necessary, then go to step 12. If test light lights, turn ignition off. Disconnect appropriate VCM connector connected to 1-2 shift solenoid ground circuit. See «WIRING DIAGRAMS»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e) . Connect ohmmeter between 1-2 shift solenoid ground circuit at appropriate VCM connector and ground circuit at transmission 20-pin connector.
6. If resistance is less than 5 ohms, go to next step. If resistance is more than 5 ohms, check for open in 1-2 shift solenoid ground circuit. Repair as necessary, then go to step 12. If circuit is okay, inspect wiring for poor connections at VCM and transmission 20-pin connector. Check for possible bent, backed out, deformed or damaged terminals. Repair as necessary, then go to step 12. If terminals and connections are okay, replace VCM, then go to step 12.
7. Measure resistance between ground and 1-2 shift solenoid ground circuit at appropriate VCM connector. If resistance is more than 1000 ohms, go to next step. If resistance is less than 1000 ohms, check for short to ground in 1-2 shift solenoid ground circuit. Repair as necessary, then go to step 12. If circuit is okay, inspect wiring for poor connections at VCM and transmission 20-pin connector. Check for possible bent, backed out, deformed or damaged terminals. Repair as necessary, then go to step 12. If terminals and connections are okay, replace VCM, then go to step 12.
8. Turn ignition off. Disconnect jumper harness from VCM side of transmission 20-pin connector and install harness to transmission side of 20-pin connector. Connect ohmmeter between 1-2 shift solenoid ground circuit and ignition feed circuit at transmission 20-pin connector.
9. If resistance is 19-31 ohms, go to next step. If resistance is not 19-31 ohms, disconnect 1-2 shift solenoid connector. Measure resistance between 1-2 shift solenoid terminals. If resistance is 19-31 ohms, check for open circuit in transmission wiring harness. Repair as necessary, then go to step 12. If resistance is not 19-31 ohms, replace 1-2 shift solenoid, then go to step 12.
10. Connect ohmmeter between ground and 1-2 shift solenoid ground circuit, and between ground and 1-2 shift solenoid ignition feed circuit at transmission 20-pin connector. If resistance is more than 250 k/ohms, see DIAGNOSTIC AIDS below. If resistance is less than 250 k/ohms, go to next step.
11. Disconnect 1-2 shift solenoid connector. Measure resistance between ground and each solenoid terminal. If resistance is more than 250 k/ohms, check for short to ground in transmission wiring harness. Repair as necessary, then go to next step. If resistance is less than 250 k/ohms, replace 1-2 shift solenoid, then go to next step.
12. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Test drive vehicle. Ensure voltage decreases to zero when1-2 shift solenoid is commanded on, and voltage increases to battery voltage when commanded off. Conditions must be met for 5 seconds. Select "Specific DTC" and enter DTC "P0753". If DTC P0753 is not present, repair is complete. If DTC P0753 is still present, repeat test.

Inspect wiring for poor connections at VCM. Check for possible bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wire that could short to bare metal or other wiring. Check for broken wire inside insulation. If diagnosing for possible intermittent short or open condition, move wiring harness while observing scan tool for value change.

Note. Perform OBD system check prior to performing diagnostic procedures. For wire circuit identification, see WIRING DIAGRAMS .

The 2-3 shift solenoid (solenoid "B") is used to control fluid flow acting on 2-3 shift valve. Solenoid is a normally-open exhaust valve that is used in conjunction with 1-2 shift solenoid (solenoid "A"), to allow 4 different shifting combinations. See the SHIFT SOLENOID COMBINATIONS table. Solenoid is attached to control valve body. Ignition voltage is supplied directly to solenoid through fused circuit. VCM commands solenoid on or off through ground circuit. DTC P0758 detects a continuous open or short to ground in 2-3 shift solenoid circuit.

DTC will set under the following conditions

1. Ignition is on.
2. System voltage is 10-17 volts.
3. VCM commands solenoid on and voltage remains high (battery voltage).
4. VCM commands solenoid off and voltage remains low (zero volts).
5. All conditions are met for 5 seconds.

DTC P0758 will be stored in VCM history. MIL will light at first failure signal, VCM commands 3rd gear only, inhibits TCC engagement, freezes shift adapts from being updated and defaults to maximum line pressure.

SHIFT SOLENOID COMBINATIONS

1. 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. If DTCs P0753, P1860, P1864 and P1886 are not present, go to next step. If DTCs P0753, P0758, P1860, P1864 and P1886 are present, remove TRANS fuse from instrument panel fuse block and inspect fuse. See «WIRING DIAGRAMS»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e) . Replace fuse if necessary, and check for short to ground in wiring harness between transmission 20-pin connector and fuse. Repair wiring as necessary, then go to step 12. If fuse is okay, check for open in wiring harness between transmission 20-pin connector and fuse. Repair wire as necessary, then go to step 12.
3. Using scan tool, command 2-3 shift solenoid on and off 3 times while listening at transmission oil pan. If solenoid does not click when commanded on and off, go to next step. If solenoid clicks when commanded on and off, inspect wiring for poor connections at VCM and transmission 20-pin connector. Check for possible bent, backed out, deformed or damaged terminals. Repair as necessary, then go to step 12. If connections and terminals are okay, see DIAGNOSTIC AIDS below.
4. Turn ignition off. Disconnect transmission 20-pin connector. Install Jumper Harness (J-39775) to VCM side of transmission 20-pin connector. Connect test light between ground and 2-3 shift solenoid ignition feed circuit at transmission 20-pin connector. Turn ignition switch to ON position. DO NOT start engine.
5. If test light does not light, check for open or short to ground in ignition feed circuit of 2-3 shift solenoid. Repair as necessary, then go to step 12. If test light lights, turn ignition off. Disconnect appropriate VCM connector connected to 2-3 shift solenoid ground circuit. See «WIRING DIAGRAMS»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e) . Connect ohmmeter between 2-3 shift solenoid ground circuit at appropriate VCM connector and ground circuit at transmission 20-pin connector.
6. If resistance is less than 5 ohms, go to next step. If resistance is more than 5 ohms, check for open in 2-3 shift solenoid ground circuit. Repair as necessary, then go to step 12. If circuit is okay, inspect wiring for poor connections at VCM and transmission 20-pin connector. Check for possible bent, backed out, deformed or damaged terminals. Repair as necessary, then go to step 12. If terminals and connections are okay, replace VCM, then go to step 12.
7. Measure resistance between ground and 2-3 shift solenoid ground circuit at appropriate VCM connector. If resistance is more than 1000 ohms, go to next step. If resistance is less than 1000 ohms, check for short to ground in 2-3 shift solenoid ground circuit. Repair as necessary, then go to step 12. If circuit is okay, inspect wiring for poor connections at VCM and transmission 20-pin connector. Check for possible bent, backed out, deformed or damaged terminals. Repair as necessary, then go to step 12. If terminals and connections are okay, replace VCM, then go to step 12.
8. Turn ignition off. Disconnect jumper harness from VCM side of transmission 20-pin connector and install harness to transmission side of 20-pin connector. Connect ohmmeter between 2-3 shift solenoid ground circuit and ignition feed circuit at transmission 20-pin connector.
9. If resistance is 19-31 ohms, go to next step. If resistance is not 19-31 ohms, disconnect 2-3 shift solenoid connector. Measure resistance between 2-3 shift solenoid terminals. If resistance is 19-31 ohms, check for open circuit in transmission wiring harness. Repair as necessary, then go to step 12. If resistance is not 19-31 ohms, replace 2-3 shift solenoid, then go to step 12.
10. Connect ohmmeter between ground and 2-3 shift solenoid ground circuit, and between ground and 2-3 shift solenoid ignition feed circuit at transmission 20-pin connector. If resistance is more than 250 k/ohms, see DIAGNOSTIC AIDS below. If resistance is less than 250 k/ohms, go to next step.
11. Disconnect 2-3 shift solenoid connector. Measure resistance between ground and each solenoid terminal. If resistance is more than 250 k/ohms, check for short to ground in transmission wiring harness. Repair as necessary, then go to next step. If resistance is less than 250 k/ohms, replace 2-3 shift solenoid, then go to next step.
12. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Test drive vehicle. Ensure voltage decreases to zero when2-3 shift solenoid is commanded on, and voltage increases to battery voltage when commanded off. Conditions must be met for 5 seconds. Select "Specific DTC" and enter DTC "P0758". If DTC P0758 is not present, repair is complete. If DTC P0758 is still present, repeat test.

Inspect wiring for poor connections at VCM. Check for possible bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wire that could short to bare metal or other wiring. Check for broken wire inside insulation. If diagnosing for possible intermittent short or open condition, move wiring harness while observing scan tool for value change.

P1875, 4WD LOW CIRCUIT MALFUNCTION

Note. Perform OBD system check prior to performing diagnostic procedures. For wire circuit identification, see WIRING DIAGRAMS .

Circuit Description ("C" & "K" Series Vehicles)

The 4WD low circuit consists of a transfer case switch, a front axle switch and a front axle actuator. When 4WD low is engaged, voltage to VCM changes from ignition voltage to zero. The 4WD low switch signal corrects transmission output speed signal to VCM. This signal compensates for transfer case gear reduction. VCM uses transmission output speed signal to adjust shift points, line pressure and TCC scheduling. DTC P1875 detects a continuous open or short to ground in 4WD circuit.

"S" & "T" Series Vehicles With 4.3L & Electric Shift

The 4WD low circuit consists of a transfer case selector switch, Transfer Case Control Module (TCCM) and wiring. When 4WD low is selected, TCCM receives a momentary signal from selector switch. If all conditions for 4WD low are met, TCCM allows electric motor in transfer case to perform shift. When 4WD low is engaged, voltage to VCM changes from ignition voltage to zero. The 4WD low switch signal corrects transmission output speed signal to VCM. This signal compensates for transfer case gear reduction. VCM uses transmission output speed signal to adjust shift points, line pressure and TCC scheduling. DTC P1875 detects a continuous open or short to ground in 4WD circuit.

"S" & "T" Series Vehicles With 4.3L & Manual Shift

The 4WD low circuit consists of a 4WD indicator assembly, selector quadrant switch, a front axle switch and wiring. When selector quadrant switch is moved to 4 low, 4WD indicator light glows and voltage to VCM changes from ignition voltage to zero. Front axle switch does not affect circuit signal input to VCM because switch is also closed in 4WD high position. The 4WD low switch signal corrects transmission output speed signal to VCM. This signal compensates for transfer case gear reduction. VCM uses transmission output speed signal to adjust shift points, line pressure and TCC scheduling. DTC P1875 detects a continuous open or short to ground in 4WD circuit.

Conditions For Setting DTC P1875

DTC will set under the following conditions

1. DTCs P0121, P0122 or P0123 (throttle position sensor) are not present.
2. DTC P0502 (vehicle speed sensor) is not present.
3. DTC P0742 (TCC stuck on) is not present.
4. DTC P0753 (1-2 shift solenoid) is not present.
5. DTC P0758 (2-3 shift solenoid) is not present.
6. DTC P1810 (trans. fluid pressure switch) is not present.
7. DTC P1860 (TCC PWM solenoid) is not present.
8. DTC P1864 (TCC solenoid) is not present.
9. Engine speed is more than 400 RPM for 8 seconds.
10. Not in fuel cutoff mode.
11. Gear range is D4.
12. Throttle angle is 17-50 percent.
13. Transmission fluid temperature is 68-248°F (20-120°C).
14. All of the above conditions are met and either of the following fail conditions occur

1. 4WD low is stuck on for 5 seconds.
2. TCC slip speed is -50 to -3000 RPM.
3. 4WD low is engaged.
4. Speed ratio (engine speed divided by transfer case output speed) is .8-1.2.

1. 4WD low is stuck off for 10 seconds.
2. TCC is commanded on.
3. TCC slip speed is 100-3000 RPM.
4. 4WD low is not engaged.
5. Speed ratio is 2.5-2.9.

DTC P1875 will be stored in VCM history. MIL will light at first failure signal, VCM commands a soft landing into 3rd gear, inhibits TCC engagement, freezes shift adapts from being updated and defaults to maximum line pressure.

Diagnostic Procedures ("C" & "K" Series Vehicles)

1. 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. Set parking brake and block drive wheels. Shift transmission into Neutral. While observing scan tool 4WD low display, select 4HI on transfer case selector switch, then select 4LO on transfer case selector switch. If scan tool 4WD low does not display NO when 4HI is selected and YES when 4LO is selected, go to next step. If scan tool 4WD low displays NO when 4HI is selected and YES when 4LO is selected, see DIAGNOSTIC AIDS below.
3. Turn ignition off. Disconnect transfer case switch connector. Turn ignition switch to ON position. If scan tool 4WD low does not indicate YES, go to next step. If scan tool 4WD low indicates YES, check for short to ground in Gray/Black wire. Repair as necessary, then go to step 6. If wire is okay, check VCM connector for possible bent, backed out, deformed or damaged terminals. Repair as necessary, then go to step 6. If terminals and connections are okay, replace VCM, then go to step 6.
4. Connect terminal "B" (Gray/Black wire) of transfer case selector switch connector to good known ground. Observe scan tool 4WD low. If scan tool 4WD low indicates YES when circuit is grounded, replace transfer case selector switch, then go to step 6.
5. If scan tool 4WD low does not indicate YES when circuit is grounded, check for open in Gray/Black wire. Repair as necessary, then go to next step. If wire is okay, check VCM connector for possible bent, backed out, deformed or damaged terminals. Repair as necessary, then go to next step. If terminals and connections are okay, replace VCM, then go to next step.
6. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Operate vehicle under following conditions. Select 4LO on selector switch. Drive vehicle. Speed ratio must be 2.5-3.0 for 5 seconds. Select 4HI on selector switch. Drive vehicle. Speed ratio must be .8-1.2 for 5 seconds. Select "Specific DTC" and enter DTC "P1875". If DTC P1875 is not present, repair is complete. If DTC P1875 is still present, repeat test.

Inspect wiring for poor connections at VCM. Check for possible bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wire that could short to bare metal or other wiring. Check for broken wire inside insulation. If diagnosing for possible intermittent short or open condition, move wiring harness while observing scan tool for value change.

1. 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. Set parking brake and block drive wheels. Shift transmission into Neutral. While observing scan tool 4WD low display, select 4HI on transfer case selector switch, then select 4LO on transfer case selector switch. If scan tool 4WD low does not display NO when 4HI is selected and YES when 4LO is selected, go to next step. If scan tool 4WD low displays NO when 4HI is selected and YES when 4LO is selected, see DIAGNOSTIC AIDS below.
3. Turn ignition off. Disconnect TCCM connector. Turn ignition switch to ON position. Connect test light between ground and Dark Green/White wire terminal at TCCM connector. Select 4LO, then 4HI on transfer case selector switch. If test light does not light when 4LO is selected and lights when 4HI is selected, go to next step. If test light lights when 4LO low is selected and turns off when 4HI is selected, go to step 7.
4. Connect test light between ground and Dark Green/White wire at transfer case selector switch. Select 4LO, then 4HI on selector switch. If test light does not light when 4LO is selected and lights when 4HI is selected, go to next step. If test light lights when 4LO is selected and turns off when 4HI is selected, go to step 6.
5. Connect test light between ground and Pink wire of transfer case selector switch. If test light lights, replace transfer case selector switch, then go to step 9. If test light does not light, check for open or short to ground in ignition feed circuit to transfer case selector switch. Repair circuit as necessary, then go to step 9.
6. Check for open or short to ground in Dark Green/White wire between transfer case selector switch and TCCM. Repair as necessary, then go to step 9.
7. Install a fused jumper between TCCM connector terminals (Dark Green/White wire and Gray/Black wire). If scan tool 4WD low displays YES, replace TCCM, then go to step 9. If scan tool 4WD low does not display YES, turn ignition off. Disconnect appropriate VCM connector connected to 4WD low indicator signal circuit. Refer to the «WIRING DIAGRAMS»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e) . Connect test light between ground and 4WD low indicator signal circuit terminal at VCM connector. If test light lights, go to next step. If test light does not light, check for open or short to ground in 4WD low indicator signal circuit. Repair circuit as necessary, then go to step 9.
8. Check VCM connector for possible bent, backed out, deformed or damaged terminals. Repair as necessary, then go to next step. If terminals and connections are okay, replace VCM, then go to next step.
9. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Operate vehicle under following conditions. Select 4LO on selector switch. Drive vehicle. Speed ratio must be 2.5-3.0 for 5 seconds. Select 4HI on selector switch. Drive vehicle. Speed ratio must be .8-1.2 for 5 seconds. Select "Specific DTC" and enter DTC "P1875". If DTC P1875 is not present, repair is complete. If DTC P1875 is still present, repeat test.

Inspect wiring for poor connections at VCM. Check for possible bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wire that could short to bare metal or other wiring. Check for broken wire inside insulation. If diagnosing for possible intermittent short or open condition, move wiring harness while observing scan tool for value change.

1. 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. Set parking brake and block drive wheels. Shift transmission into Neutral. While observing scan tool 4WD low display, select 4HI on selector quadrant switch, then select 4LO on selector quadrant switch. If scan tool 4WD low does not display NO when 4HI is selected and YES when 4LO is selected, go to next step. If scan tool 4WD low displays NO when 4HI is selected and YES when 4LO is selected, see DIAGNOSTIC AIDS below.
3. Place selector quadrant switch in 4HI position. Using a DVOM, backprobe between ground and voltage input connector (Gray/Black wire) at 4WD indicator assembly. If voltage is 9.6-12.6 volts, go to next step. If voltage is not 9.6-12.6 volts, check for open or short to ground in Gray/Black wire. Repair wire as necessary, then go to step 9. If wire is okay, replace selector quadrant switch, then go to step 9.
4. Place selector quadrant switch in 4LO position. Using a DVOM, backprobe between ground and terminal No. 5 at selector quadrant switch connector to 4WD indicator assembly. If voltage is more than .5 volts, go to next step. If voltage is less than .5 volts, go to step 8.
5. Disconnect selector quadrant switch connector and voltage input connector from 4WD indicator assembly. Using an ohmmeter, measure resistance between voltage input connector terminal No. 5 on 4WD indicator assembly circuit board and selector quadrant switch terminal No. 5 on circuit board. If resistance is less than one ohm, go to next step. If resistance is more than one ohm, replace 4WD indicator assembly, then go step 9.
6. Measure resistance between voltage input connector terminal No. 2 on 4WD indicator assembly circuit board and selector quadrant switch terminal No. 6 on circuit board. If resistance is less than one ohm, go to next step. If resistance is more than one ohm, replace 4WD indicator assembly, then go step 9.
7. Check for open in Black wire (ground circuit) of 4WD indicator assembly. Repair wire as necessary, then go to step 9. If wire is okay, replace 4WD indicator assembly, then go to step 9.
8. Check VCM connector for possible bent, backed out, deformed or damaged terminals. Repair as necessary, then go to next step. If terminals and connections are okay, replace VCM, then go to next step.
9. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Operate vehicle under following conditions. Select 4LO on selector quadrant switch. Drive vehicle. Speed ratio must be 2.5-3.0 for 5 seconds. Select 4HI on selector quadrant switch. Drive vehicle. Speed ratio must be .8-1.2 for 5 seconds. Select "Specific DTC" and enter DTC "P1875". If DTC P1875 is not present, repair is complete. If DTC P1875 is still present, repeat test.

Inspect wiring for poor connections at VCM. Check for possible bent, backed out, deformed or damaged terminals. Check for weak terminal tension. Check for chafed wire that could short to bare metal or other wiring. Check for broken wire inside insulation. If diagnosing for possible intermittent short or open condition, move wiring harness while observing scan tool for value change.

COMPONENT & WIRING HARNESS RESISTANCE CHECK

1. Install Jumper Harness (J-39775) to transmission 20-pin connector. Using an ohmmeter, measure resistance between specified terminals for each component. (Scheme 36) Compare resistance reading to known values. See «TRANSMISSION COMPONENT RESISTANCE SPECIFICATIONS»(/chevrolet/blazer/s15-1994-1998/remont/automatic-trans/#automatic-transmission-diagnosis-4l60-e) table.
2. If resistance reading is okay, go to next step. If resistance reading is not okay, disconnect wiring harness at component and measure component resistance. Replace component if resistance is not as specified. If resistance is as specified, repair wiring harness between component and 20-pin connector.
3. Measure resistance between ground and each terminal at transmission 20-pin connector. (Scheme 36) Resistance should be more than 250 k/ohms for each solenoid and more than 10 megohms for fluid temperature and vehicle speed sensors. Resistance for fluid temperature sensor will vary with temperature. If resistance is within specification, problem is intermittent. If resistance is low, disconnect wiring harness at component.
4. Measure resistance between component terminals and ground. If resistance is low, replace component. If resistance is high, inspect wiring harness for short to ground. Repair as necessary.

PRESSURE SWITCH ASSEMBLY

Install Jumper Harness (J39775) to transmission 20-pin connector. Compare resistance of pressure switches with gear selector in each position to known values. (Scheme 37) If resistance values are the same as chart, problem is intermittent. If resistance values are not the same, complete chart until problem is found.

TRANSMISSION COMPONENT RESISTANCE SPECIFICATIONS

Identifying Component & Connector Terminal Locations Courtesy of General Motors Corp. Scheme 36

Pressure Switch Assembly Resistance Chart Courtesy of General Motors Corp. Scheme 37

1996 "B" Body - 4.3L & 5.7L (Caprice, Impala SS & Roadmaster) Wiring Diagram. Scheme 38

1996 "D" Body - 5.7L (Fleetwood) Wiring Diagram. Scheme 39

1996 "F" Body - 3.8L (Camaro & Firebird) Wiring Diagram. Scheme 40

1996 "F" Body - 5.7L (Camaro & Firebird) Wiring Diagram. Scheme 41

1996 "Y" Body - 5.7L (Corvette) Wiring Diagram. Scheme 42

1996 "C" & "K" Series - 4.3L, 5.0L & 5.7L (Pickup, Sierra, Suburban, Tahoe & Yukon) Wiring Diagram. Scheme 43

1996 "G" Series - 4.3L, 5.0L & 5.7L (Van) Wiring Diagram. Scheme 44

1996 "L" & "M" Series - 4.3L (Astro & Safari) Wiring Diagram. Scheme 45

1996 "S" & "T" Series - 2.2L (Pickup & Sonoma) Wiring Diagram. Scheme 46

1996 "S" & "T" Series - 4.3L (Blazer, Bravada, Jimmy, Pickup & Sonoma) Wiring Diagram. Scheme 47

See also:
• CLUTCH & BAND APPLICATION
• APPLICATION
• COMPONENT TESTS
• CLEARING TROUBLE CODES
• P0502
• P0560
• P0712
• P0713
• P0719
• P0724
• P0742
• P0748
• P0751
• P0753
• P0756
• P0758
• P1572
• P1810
• P1812
• P1860
• P1864
• P1870
• P1873
• P1874
• P1886
• P0502
• P1875
• RETRIEVING CODES
• EEPROM REPROGRAMMING