Automatic Transmission - Diagnosis - 4l80-e Chevrolet Cab & Chassis K3500

APPLICATION

THM 4L80-E APPLICATION

1993-94 SERIES CODE DESIGNATIONS

DESCRIPTION

The 4L80-E transmission uses 2 electric shift solenoids to control transmission upshifts and downshifts. In addition, a force motor (also referred to as pressure control solenoid) controls hydraulic line pressure, and a Torque Converter Clutch (TCC) solenoid controls TCC application. Solenoid is turned on and off by the Powertrain Control Module (PCM) or Transmission Control Module (TCM). PCM/TCM has on-board self-diagnostics to help identify any components or circuits that may need further testing.

OPERATION

Shift solenoid holds hydraulic pressure when it is on and releases pressure when it is off. This action controls the 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 CHART table under ELECTRONIC TESTING.

PCM/TCM

Note. Models with gasoline engines use a Powertrain Control Module (PCM) computer. Models with diesel engines use a Transmission Control Module (TCM) computer. These computers control TCC, force motor (hydraulic pressure) and shift solenoids "A" and "B".

The PCM/TCM is located behind driver's seat riser ("G" Series Van and "P" Series Commercial Van) or behind right side of dash on all other vehicles. On "G" Series Van Motorhome, PCM/TCM has been relocated to behind left side "B" pillar. PCM/TCM controls TCC, force motor (hydraulic pressure) and shift solenoids "A" and "B". In addition, PCM also controls ignition, fuel and emission devices related to the engine.

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

SENSORS & SWITCHES

The PCM/TCM controls upshifts and downshifts based on coolant temperature, transmission fluid temperature, system voltage, throttle position, transmission oil pressure switches, and transmission output and input speed sensors. (Scheme 71) The system includes several other switches and sensors that are used for engine control (gasoline engines). For additional information and testing of engine components, see appropriate article in ENGINE PERFORMANCE of appropriate MITCHELL(R) manual.

Shift Solenoids "A" & "B"

Transmission is shifted up or down by 2 electric solenoids. Both solenoids are located on valve body. (Scheme 71) Ignition power is supplied to each solenoid by the transmission fuse. Solenoid "A" controls hydraulic pressure to 1-2 and 3-4 shift valves (if equipped). Solenoid "B" controls hydraulic pressure to 2-3 shift valve.

Force Motor (Pressure Control Solenoid)

Force motor solenoid has a spool valve and operates pressure regulator valve. (Scheme 71) The computer sends a frequency signal to the force motor to regulate hydraulic line pressure. The frequency signal (duty cycle) is measured with a dwell meter or lab scope. When the duty cycle is zero, line pressure is at maximum, and force motor draws zero amp. When the duty cycle is 40 percent, line pressure is at minimum, and force motor draws 1.1 amps at 4-5 volts.

TCC (PWM) Solenoid

This solenoid is used to control TCC apply valve. The computer sends a frequency signal to the TCC solenoid to gradually apply or release the TCC. (Scheme 71)

Scheme 71

TORQUE CONVERTER CLUTCH (TCC) CONTROL COMPONENTS

Note. PCM may also be referred to as ECM.

The following components are used in TCC system. Not all components will be present on all vehicles.

Brake Switch

Power from ignition switch passes through brake switch to TCC solenoid. When brake pedal is depressed with TCC engaged, power to TCC solenoid is interrupted, releasing converter clutch and preventing engine from stalling.

Coolant Temperature Sensor

This sensor provides PCM with engine coolant temperature information. PCM will not allow TCC operation until signal from this sensor indicates coolant temperature greater than 130-150°F (55-65°C).

Powertrain Control Module (PCM)

To determine application of torque converter clutch, PCM receives and processes information from various input devices. These devices may include the vehicle speed sensor, coolant temperature sensor, throttle position sensor and brake switch. The PCM controls application of torque converter clutch by providing a ground circuit for the TCC solenoid circuit.

TCC Solenoid Assembly

Solenoid is energized by PCM to redirect transmission fluid to the converter clutch apply valve in the auxiliary control valve assembly.

Acts with TCC regulator valve to control the apply and release of TCC.

Throttle Position Sensor (TPS)

Provides PCM with throttle position information. TCC operation is prevented when throttle position signal is less than a specified value.

Vacuum Sensor

Sends engine vacuum (load) information to PCM.

Vehicle Speed Sensor (VSS)

This sensor sends vehicle speed information to PCM. Vehicle speed must be greater than a certain value before TCC can be applied. Two types of speed sensor are used. A light emitting diode type is used in the instrument cluster on some models. Other models use a Permanent Magnet (PM) generator mounted in the transmission.

Note. Diagnostic codes for coolant temperature sensor, throttle position sensor or vehicle speed sensor may be present while performing TCC electrical diagnosis. See ENGINE PERFORMANCE in appropriate MITCHELL(R) manual for complete information on General Motors Computerized Engine Control systems.

SELF-DIAGNOSTICS

PCM/TCM constantly monitors all electrical circuits. If PCM/TCM detects circuit problem(s) or out-of-range sensor(s), a Diagnostic Trouble Code (DTC) will be recorded in computer memory. If problem continues for a preset time, the Malfunction Indicator Light (MIL) or SERVICE ENGINE SOON light will glow.

If the MIL (SERVICE ENGINE SOON) light is always on, DTC is currently being detected. If the MIL (SERVICE ENGINE SOON) light is off, but PCM/TCM has detected a circuit or sensor problem, DTC's will be stored in computer memory.

Stored DTC's may be retrieved from PCM/TCM memory using scan tool or MIL (SERVICE ENGINE SOON) light. See appropriate RETRIEVING CODES procedure under ELECTRONIC SELF-DIAGNOSTICS.

Note. For complete PCM/TCM testing and diagnosis, see appropriate article in ENGINE PERFORMANCE of appropriate MITCHELL(R) manual.

CLUTCH & BAND APPLICATION TABLE

CLUTCH & BAND APPLICATION

ELECTRONIC SELF-DIAGNOSTICS

Note. To test electronic control of transmission solenoids without using self-diagnostics, go to COMPONENT TEST CHARTS (NO CODES) under ELECTRONIC TESTING. After repairs are made, trouble codes should be erased from computer memory. See CLEARING TROUBLE CODES under ELECTRONIC SELF-DIAGNOSTICS.

RETRIEVING CODES (WITHOUT SCAN TOOL)

Note. The Assembly Line Data Link (ALDL) may also be referred to as the Data Link Connector (DLC).

Scheme 72

1. With key on and engine off, locate Assembly Line Data Link (ALDL) connector under dash, on driver's side of vehicle. Connect a jumper wire between ALDL terminal "B" (test terminal) and terminal "A" (ground terminal). (Scheme 72) This places control module in diagnostic mode. NOTE: Connecting terminals "A" and "B" of ALDL connector with engine running will cause fuel injected vehicles to enter field service mode. The MIL (SERVICE ENGINE SOON) light will not flash codes if this is done.
2. In this mode, control module will display DTC 12 by flashing MIL (SERVICE ENGINE SOON) light. DTC 12 is identified by MIL (SERVICE ENGINE SOON) light flashing once, followed by a short pause, then 2 flashes in quick succession.
3. Each DTC will be repeated 3 times. DTC 21 is identified by 2 flashes, a short pause followed by one flash; DTC 53 is identified by 5 flashes, a short pause followed by 3 flashes. DTC's are separated by slightly longer pauses.
4. DTC's are displayed in numerical order. Each code is displayed 3 times. DTC's will continue to repeat as long as ALDL test terminal is grounded. If DTC's are not flashed, or MIL (SERVICE ENGINE SOON) light does not glow, self-diagnostics will not work. See CHART A-1 under DIAGNOSTIC CHARTS.
5. If MIL (SERVICE LIGHT SOON) light glows steadily, see CHARTA-2 under DIAGNOSTIC CHARTS. To exit diagnostic mode, turn ignition off, and remove jumper wire from ALDL connector.

Note. DTC's will be recorded at various operating times. Some codes require operation of 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, but may require road testing vehicle in order to duplicate condition under which code will set.

RETRIEVING CODES (WITH SCAN TOOL)

Note. To read DTC's and check system voltages on serial data line, plug scan tool into ALDL.

The scan tool is a specialized tester which, when plugged into ALDL, can be used to diagnose on-board computer control systems by providing instant access to circuit voltage information without need to crawl under dash or hood to backprobe sensors and connectors.

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 the control module. It does not indicate if devices have responded properly to that signal. This will need to be checked at output device using a voltmeter or test light.

Note. DTC 12 should always exist when ALDL is grounded with key on and engine off, but may not be indicated by all makes of scan tools.

If DTC is not present, this is not an indication that there is no problem. 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.

Out-of-specification sensors WILL NOT set trouble code, but WILL cause driveability problems. Using scan tool is the easiest method of checking sensor specifications and other data parameters. Intermittent wiring problems may be identified by wiggling wiring harnesses and connections (key on, engine off) while observing scan tool.

Note. If erroneous voltage signals are suspected, it will be necessary to verify tester information using digital voltmeter and wiring schematic. If non-existent codes are displayed, turn ignition off, remove scan tool, turn ignition on, and ground ALDL test terminal "B". The same codes should be retrieved whether scan tool or MIL (SERVICE ENGINE SOON) light is used.

TROUBLE CODE DEFINITION

PCM/TCM TROUBLE CODE DEFINITION

Note. Only transmission-related trouble codes are listed. If other trouble codes are present, see appropriate article in ENGINE PERFORMANCE of appropriate MITCHELL(R) manual.

HARD OR INTERMITTENT TROUBLE CODE DETERMINATION

During any diagnostic procedure, it must be determined if codes are hard failure codes or intermittent failure codes. A hard failure indicates that a problem is currently present. Diagnostic charts do not usually provide intermittent code diagnosis. To determine hard codes and intermittent codes, proceed as follows

1. Manually enter diagnostic mode. Record all stored trouble codes. Exit diagnostic mode, and clear trouble codes. See CLEARING TROUBLE CODES.
2. Apply parking brake and place transmission in Neutral or Park. Block drive wheels and start engine. MIL (SERVICE ENGINE SOON) light should go out. Operate warm engine at specified curb idle for 2 minutes, and note MIL (SERVICE ENGINE SOON) light.
3. If MIL (SERVICE ENGINE SOON) light does not come on, codes are intermittent failures. If MIL (SERVICE ENGINE SOON) light comes on, manually enter diagnostic mode. Record trouble codes. If same codes reappear, they are hard failure codes. It may be necessary to road test vehicle in order to reset hard failure codes.

CLEARING TROUBLE CODES

Trouble codes should be cleared after repairs have been completed. Also, some diagnostic charts require that codes be cleared before using diagnostic chart. To clear codes, disconnect PCM/TCM power feed for 30 seconds.

DIAGNOSTIC CHARTS

The following charts include flow charts, testing information and related wiring diagram. Terminal numbers and wire colors may vary depending on model. For complete transmission wiring diagrams, see WIRING DIAGRAMS. For additional engine diagnostic information, see appropriate article in ENGINE PERFORMANCE of appropriate MITCHELL(R) manual.

Note. Some charts require the use of a bidirectional (Tech 1) scan tool. If a bidirectional scan tool is not available, the PCM/TCM-controlled relays and solenoids may be energized by grounding ALDL test terminal "B" with ignition on and engine off. DIAGNOSTIC AIDS in charts may help diagnose trouble codes when problem cannot be identified through circuit checks.

CHART A-1, NO MIL (SERVICE ENGINE SOON) LIGHT

MIL (SERVICE ENGINE SOON) light should be on when engine is off and ignition is on. Switching battery voltage is supplied to MIL. The PCM turns light on by providing a ground path through circuit No. 419/1234.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) If fusible link or fuse is blown, refer to WIRING DIAGRAMS to identify related circuits.

Test Number 2) Using a test light connected to 12 volts, probe each PCM/TCM ground circuit and ensure continuity to ground is present.

Diagnostic Aids

If engine runs okay, check for faulty light bulb. Check for open circuit No. 419/1234 or blown ALT or GAUGES fuse. A blown fuse will also cause instrument panel-mounted warning lights not to work.

Scheme 73

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Scheme 75

Scheme 76

CHART A-2, NO ALDL DATA, NO DTC 12 OR MIL (SERVICE ENGINE SOON) LIGHT ON

MIL (SERVICE ENGINE SOON) light should be on when engine is off and ignition is on. Switching battery voltage is supplied to MIL. The PCM turns light on by providing a ground path through circuit No 419/1234. With diagnostic terminal grounded, MIL (SERVICE ENGINE SOON) light should flash DTC 12, followed by any other DTC stored in memory. A steady light on indicates a short to ground in circuit No. 419/1234, or no engine speed sensor signal.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) If there is a problem with PCM/TCM that causes scan tool not to read serial data, then the PCM/TCM should not flash DTC 12. If DTC 12 does not flash, ensure scan tool is functioning properly by testing on another vehicle. If scan tool and circuit No. 1061 are okay, PCM/TCM or PROM may be cause of no ALDL data.

Test Number 2) If light goes off (with PCM/TCM disconnected), circuit No. 419/1234 is not shorted to ground.

Test Number 3) This step checks for open diagnostic circuit No. 451.

Test Number 4) MIL light control circuit is okay. Problem is a faulty PCM/TCM or PROM. If DTC 12 does not flash, the PCM/TCM should be replaced using the original PROM. Replace PROM only after trying aPCM/TCM. A defective PROM usually is an unlikely cause of the problem.

Scheme 77

DTC 14, COOLANT TEMPERATURE SENSOR HIGH TEMPERATURE INDICATED (SIGNAL VOLTAGE LOW)

PCM uses coolant temperature sensor inputs in determining control of fuel delivery, engine timing, idle and converter clutch (TCC). As engine warms, sensor resistance reduces. At normal operating temperature, voltage signal will be about 1.5-2.0 volts at PCM coolant sensor terminals.

Note. For 1994 gasoline, see appropriate wiring diagram under WIRING DIAGRAMS. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This checks if conditions for DTC 14 still exist. DTC 14 indicates control module has sensed low coolant sensor voltage signal (high temperature) at control module terminal for 6 seconds.

Test Number 2) This tests for grounded sensor signal line between control module and coolant sensor.

After engine is started, temperature should rise steadily to about 194°F (90°C), then stabilize when thermostat opens. If engine is allowed to cool overnight, coolant temperature sensor and MAT sensor (if equipped) should read close to each other, when measured with a scan tool. Measure sensor resistance to check for shifted calibration. See TEMPERATURE-TO-RESISTANCE VALUES (DTC 14) table.

TEMPERATURE-TO-RESISTANCE VALUES (1) (2) (DTC 14)

Scheme 78

Scheme 79

Scheme 80

Scheme 81

DTC 15, COOLANT TEMPERATURE SENSOR LOW TEMPERATURE INDICATED (SIGNAL VOLTAGE HIGH)

PCM uses coolant temperature sensor inputs in determining control of fuel delivery, engine timing, idle and converter clutch (TCC). As engine warms, sensor resistance reduces and voltage drops. At normal operating temperature, voltage signal will be about 1.5-2.0 volts at PCM coolant sensor signal terminal. If sensor signal circuit opens, PCM will see -40°F (-40°C) and deliver fuel for this temperature.

Note. For 1994 gasoline, see appropriate wiring diagram under WIRING DIAGRAMS. Test numbers refer to test numbers on diagnostic chart.

Test Number 1) This checks if conditions for DTC 15 still exist. DTC 15 indicates control module has sensed high resistance in coolant sensor circuit. This could be due to high resistance (low temperature) or high voltage at coolant sensor terminal at control module for one second.

Test Number 2) This test simulates conditions for DTC 14. If control module recognizes low voltage signal, scan tool will display temperature greater than 266°F (130°C), indicating control module and wiring are not at fault.

Test Number 3) This test determines if coolant sensor ground or signal circuit is open. There should be 5 volts present at sensor connector.

After engine is started, temperature should rise steadily to about 194°F (90°C) then stabilize when thermostat opens. If engine is allowed to cool overnight, coolant temperature sensor and MAT sensor (if equipped) should read close to each other, when measured with a scan tool. Measure sensor resistance to check for shifted calibration. See TEMPERATURE-TO-RESISTANCE VALUES (DTC 15) table.

TEMPERATURE-TO-RESISTANCE VALUES (1) (2) (DTC 15)

Scheme 82

DTC 21, THROTTLE POSITION SENSOR SIGNAL VOLTAGE HIGH

Throttle Position Sensor (TPS) provides a varying voltage signal depending on throttle valve angle. Signal voltage varies from about .50 volt at idle to 4.5 volts at wide open throttle. Each time TPS voltage drops to less than 1.25 volts and stops, PCM assumes this is zero degrees throttle angle and measures throttle percentage angle from this point. When DTC 21 sets, the following occurs

1. Torque converter clutch will not be applied.
2. Pressure control solenoid current will be low, resulting in high line pressure.
3. Fixed or harsh shift points, and no 4th gear when hot.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) DTC 21 sets if TP signal voltage is greater than 4.9 volts at WOT for 4 seconds.

Test Number 2) With TP sensor disconnected, TP voltage should go low if the PCM and wiring are okay.

Test Number 3) Probing circuit No. 452 with a test light checks 5-volt return circuit.

Scan tool displays throttle position in volts. Closed throttle voltage should be low. As throttle angle increase, voltage should increase gradually to about 4.5 volts at a steady rate.

Scheme 83

Scheme 84

Scheme 85

Scheme 86

DTC 21/22, THROTTLE POSITION SENSOR SIGNAL VOLTAGE LOW/HIGH (1994) DIESEL

Throttle Position Sensor (TPS) provides a varying voltage signal depending on throttle valve angle. Signal voltage varies from about .50 volt at idle to 4.5 volts at wide open throttle.

DTC 21 will set when engine is operating, TP sensor signal voltage is greater than 4.9 volts and condition is met for one second.

DTC 22 will set when engine is operating, TP sensor signal voltage is less than .2 volt and condition is met for one second. PCM will default to maximum line pressure, 35 percent throttle and inhibit 4th gear if in hot mode.

Note. Test numbers refer to test numbers on diagnostic chart.

Test Number 1) This test checks for presence of 5 volts at TP sensor.

Test Number 2) Scan tool should display 5 volts reference to TCM.

TP sensor voltage should increase smoothly as accelerator pedal is applied. If an intermittent is suspected, check terminal tension at TP sensor and TCM. Also, use snapshot mode on scan tool to trigger this DTC.

Scheme 87

Scheme 88

DTC 22, THROTTLE POSITION SENSOR SIGNAL VOLTAGE LOW

Throttle Position Sensor (TPS) provides a varying voltage signal depending on throttle valve angle. Signal voltage varies from about .50 volt at idle to 4.5 volts at wide open throttle. When DTC 22 sets, the following occurs

1. Torque converter clutch will not be applied.
2. Pressure control solenoid current will be low, resulting in high line pressure and harsh shifts.

Note. Test numbers refer to test numbers on diagnostic chart.

Test Number 1) DTC 22 will set if TP signal voltage is less than .06 volt for 4 seconds.

Test Number 2) This test simulates conditions for DTC 21. If control module recognizes state change, control module and wiring are okay.

Test Number 3) This simulates high signal voltage to check for open in TPS signal line to control module. Scan tool should recognize signal and display high TPS voltage.

Scan tool displays throttle position in volts. Closed throttle voltage should be low. As throttle angle increases, voltage should increase gradually to about 4.5 volts at a steady rate. Open or short to ground in circuits No. 416 or 417 will set DTC 22.

Scheme 89

DTC 24, OUTPUT SPEED SENSOR LOW (1993 2WD)

The speed sensor, which is a Permanent Magnet (PM) generator, provides Digital Ratio Adapter Control (DRAC) with vehicle speed information. PM generator, mounted in transmission, produces a pulsing voltage signal whenever vehicle speed is more than 3 MPH. Voltage level and pulse increase with vehicle speed. DRAC converts PM generator signal to a pulsing signal by grounding circuit No. 437 (Brown wire) 2000 times per mile. Control module uses this signal in calculations to determine vehicle adjustments.

DTC 24 will set under following conditions: vehicle speed is zero, transmission is not in Park or Neutral, engine speed is greater than 3000 RPM, and PCM/TCM input circuit No. 437 is constant. All of these conditions must be met for 1.5 seconds. PM generator only produces voltage signal if drive wheels are turning faster than 3 MPH.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This tests for voltage variation while wheels are turning. Voltage will be low at low wheel speeds (4-6 volts at 20 MPH).

Test Number 2) This step determines whether VSS assembly is faulty, circuit No. 437 is grounded, or PCM/TCM connector or PCM/TCM is faulty.

Test Number 3) This signal indicates an open circuit No. 437 or faulty DRAC.

Test Number 4) This is a normal voltage signal.

Using scan tool, check for proper signal in Drive while wiggling wiring. Ensure all connectors are good. Check the pass-through connector at transmission.

Scheme 90

Scheme 91

DTC 24, OUTPUT SPEED SENSOR LOW (1993 4WD)

The speed sensor, which is a Permanent Magnet (PM) generator, provides PCM/TCM with vehicle speed information. PM generator, mounted in transfer case, produces a pulsing voltage signal whenever vehicle speed is greater than 3 MPH. Control module uses this signal in calculations to determine vehicle adjustments.

DTC 24 will set under following conditions: vehicle speed is less than 20 MPH, transmission is not in Park or Neutral, and engine speed is greater than 3000 RPM. All of these conditions must be met for 1.5 seconds. PM generator only produces voltage signal if drive wheels are turning faster than 3 MPH.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This step tests for voltage variation while wheels are turning. Voltage will be low at low wheel speeds (4-6 volts at 20 MPH).

Test Number 2) This step tests operation of output sensor.

Check the pass-through connector at transmission. If input sensor is not working at start-up, output sensor will read zero.

Scheme 92

Scheme 93

DTC 24 & DTC 72, VEHICLE SPEED SENSOR (OUTPUT SPEED SIGNAL LOW) & (OUTPUT SPEED SIGNAL LOSS) 1994

Speed sensor circuit consists of a magnetic induction type Vehicle Speed Sensor (VSS), a buffer module, 4WD low switch (when needed) and wiring. Gear teeth pressed on output shaft induces an alternating current into sensor when wheels are turning. This signal is transmitted to the buffer module. The buffer module compensates for various final drive ratios. The buffer module will also convert the A/C VSS signal into a 40 pulse per revolution D/C signal on circuit No. 437, to indicate transmission output speed. On 4WD vehicles, 4WD low signal will also be used for adjustment of the 40 pulse per revolution signal to PCM/TCM.

DTC 24 will set under the following conditions: DTC(s) 21, 22, 28, 33 or 34 is not present, vehicle is not in Park or Neutral, circuit No. 437 voltage is constant, engine speed is greater than 3000 RPM, output speed is less than 200 RPM, MAP pressure is greater than 5.8 psi, throttle position is between 10 percent and 100 percent, and all conditions are met for 3 seconds. PCM/TCM will default to 2nd gear only at maximum line pressure.

DTC 72 will set under the following conditions: with vehicle not in Park or Neutral, DTC 28 is not present, engine speed is greater than 300 RPM, output speed is greater than 1000 RPM, (2050 RPM in Park or Neutral) and all conditions are met for 2 seconds. PCM/TCM will default to maximum line pressure and a soft delayed shift to second gear will occur.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This test checks for voltage to buffer module.

Test Number 2) This test checks ground circuit to buffer module.

Test Number 3) This test checks VSS circuit at buffer module.

Test Number 4) This test checks for an output speed signal from buffer module.

DTC 24 will set when no vehicle speed is detected at start off. DTC 72 will set when vehicle speed has been detected and is lost during vehicle operation.

Scheme 94

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Scheme 96

DTC 28, PRESSURE SWITCH MANIFOLD (PSM) ASSEMBLY FAULT (1993)

Pressure Switch Manifold (PSM), also referred to as fluid pressure switch assembly, is actually 5 pressure switches combined into one unit and mounted on the transmission valve body. The PCM/TCM supplies battery voltage to the PSM on 3 separate wires. By grounding one or more of these circuits through various combinations of switches inside the pressure switch manifold, the PCM/TCM detects what gear range has been selected by the vehicle operator.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This step tests for proper operation of pressure switches.

Test Number 2) This step tests for correct voltage from PCM/TCM to transmission pass-through connector.

Test Number 3) This step tests for short to ground in any one of 3 pressure switch circuits.

DTC 28 will set if PCM/TCM detects one of 2 "illegal" PSM assembly combinations. See PSM COMBINATION CHART for range combinations. Check all wiring connectors for proper terminal tension and location.

PSM COMBINATION

Scheme 97

Scheme 98

DTC 28, PRESSURE SWITCH MANIFOLD (PSM) ASSEMBLY FAULT (1994)

Pressure Switch Manifold (PSM) assembly, also referred to as fluid pressure switch assembly, consists of 5 normally open pressure switches. PCM/TCM supplies battery voltage to each range signal. By grounding one or more of these circuits through various combinations of pressure switches, PCM/TCM detects what gear range has been selected by vehicle operator. With ignition on and engine off, Park/Neutral will be indicated. When transmission electrical connector is disconnected, ground potential for 3 range signals to PCM/TCM will be removed and gear selector position "D2" will be indicated.

DTC 28 will set when range signals "A" and "C" are both zero volts and condition is met for 2 seconds. PCM/TCM will default to no TCC, disable transmission manual mode, "D4" shift control and no 4th gear in hot mode.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This test checks indicated range signal to range actually selected.

Test Number 2) This test checks for correct voltage from PCM/TCM to transmission external connector.

Test Number 3) This test will detect a short to ground or an open in any one of 3 PSM assembly range circuits.

DTC 28 will set if PCM/TCM detects one of 2 "illegal" PSM assembly combinations. See PSM COMBINATION CHART for range combinations. Check all wiring connectors for proper terminal tension and location.

PSM COMBINATION

Scheme 99

Scheme 100

Scheme 101

DTC 37 & 38, TCC BRAKE SWITCH STUCK ON OR OFF (1994)

Normally closed brake switch supplies battery voltage signal on circuit No. 420 to PCM/TCM. Signal voltage drops to zero volts when TCC brake switch is opened (brake pedal depressed).

DTC 37 will set when circuit No. 420 is open, vehicle speed is less than 5 MPH for greater than 6 seconds, then vehicle speed is between 5-20 MPH for greater than 6 seconds, then vehicle speed is greater than 20 MPH for greater than 6 seconds. Conditions must occur on 7 different occasions.

DTC 38 will set when circuit No. 420 has constant voltage, vehicle speed is greater than 20 MPH for greater than 6 seconds, then vehicle speed is between 5-20 MPH for greater than 6 seconds. Conditions must occur on 7 different occasions.

For both DTC's, PCM/TCM will default to no TCC and no 4th gear in hot mode.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This test checks for voltage at brake switch.

Test Number 2) This test checks brake switch.

Test Number 3) This test checks circuit No. 420 at PCM/TCM.

Problem may be intermittent. Check brake switch connections. Check customer driving habits and/or unusual traffic conditions such as stop and go traffic conditions.

Scheme 102

Scheme 103

DTC 39, TORQUE CONVERTER CLUTCH STUCK OFF (1993)

The purpose of the automatic transmission Torque Converter Clutch (TCC) feature is to eliminate power loss of the torque converter stage when vehicle is in a cruise condition. This allows the convenience of the automatic transmission, and fuel economy of a manual transmission. Fused battery ignition voltage is supplied to the TCC solenoid, which is used inside the valve body to shift a spool valve to modulate pressure to the TCC. This modulated pressure normally allows some slight slippage of TCC.

The PCM/TCM will engage TCC by grounding circuit No. 422, energizing the solenoid. DTC 39 will set under the following conditions; TCC is engaged, TCC "slip" is greater than 65 RPM for 2 seconds or 2nd or 3rd gear is selected or indicated.

Note. Test numbers refer to test numbers on diagnostic chart.

Test Number 1) This step determines if transmission is receiving a TCC command from the pass-thru connector. If bidirectional scan tool is not available, TCC may be activated by grounding ALDL test terminal "B" with ignition on and engine off.

Test Number 2) This step checks for power to transmission.

Test Number 3) This test determines if PCM/TCM is commanding TCC to be on.

Clear codes and re-check for DTC 39. If DTC 39 resets, problem may be inside torque converter or transmission. DTC 39 will only set in 3rd gear. TCC slip in 4th gear will set DTC 68.

Scheme 104

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DTC 39, TORQUE CONVERTER CLUTCH STUCK OFF (1994)

The purpose of the automatic transmission Torque Converter Clutch (TCC) feature is to eliminate power loss of the torque converter stage when vehicle is in a cruise condition. This allows the convenience of the automatic transmission, and fuel economy of a manual transmission.

PCM/TCM commands the TCC PWM solenoid on by modulating TCC signal fluid acting on converter clutch shift valve. TCC fluid applies torque converter clutch.

DTC 39 will set when DTC(s) 28, 71 or 74 is not present, TCC is commanded on, TCC slip speed is greater than 65 RPM, transmission range switch indicates "D3" or "D4", transmission is in 2nd or 3rd gear and all conditions are met for 2 seconds. PCM/TCM will inhibit 4th gear if in hot mode.

Note. Test number refers to number on diagnostic chart.

Test Number 1) This test checks the mechanical and hydraulic operation of TCC, while commanded on by PCM/TCM.

Snapshot mode will record 5 data parameters per second.

Scheme 107

Scheme 108

DTC 51, PROM PROBLEM

Ensure all pins are fully inserted in socket. If pins are fully inserted, replace PROM and recheck. If problem is not corrected, replace PCM.

DTC 52 & 53, LONG SYSTEM VOLTAGE HIGH OR SYSTEM VOLTAGE HIGH (1994)

Ignition voltage is supplied to PCM/TCM to indicate ignition switch status. Battery voltage is supplied to PCM/TCM to maintain memory of learned functions and parameters.

DTC 52 will set when ignition is on, ignition system voltage is greater than 16 volts and conditions are met for 109 minutes. DTC 53 will set when ignition is on, ignition system voltage is greater than 19.5 volts and conditions are met for 2 minutes. PCM/TCM will default to maximum line pressure, inhibit TCC and shift transmission to 2nd gear.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) Normal battery voltage is between 9-15 volts.

Test Number 2) This test checks if alternator is faulty under load conditions. If voltage is more than 15 volts, check and repair charging system as necessary.

Jump-starting engine or charging battery may set DTC's 52 or 53. If DTC's set when an accessory is operated, check for poor connections or excessive current draw. Also check for poor connections at starter solenoid or fusible link.

Scheme 109

Scheme 110

DTC 53, SYSTEM VOLTAGE HIGH (1993)

DTC 53 will set when ignition is on and PCM/TCM 12-volt battery feed voltage is greater than 19.5 volts for about 2 seconds. During the time the failure is present, the force motor is turned off, transmission immediately shifts to 2nd gear, and TCC operation is inhibited. The setting of additional codes may result.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) Normal system charging voltage is 9-15 volts.

Test Number 2) This test checks if high voltage reading is due to the alternator, circuit No. 440 or PCM/TCM. With engine running, check voltage at battery. If voltage is greater than 15 volts, the PCM/TCM is okay.

Test Number 3) This step checks if alternator is faulty under load conditions. If voltage is greater than 15 volts, check alternator.

Jump-starting engine or charging battery may set DTC 53. If DTC is set when an accessory is operated, check for poor connections or excessive current draw. Also check for poor connections at starter solenoid or fusible link.

Scheme 111

Scheme 112

DTC 58, TRANSMISSION FLUID TEMPERATURE SENSOR CIRCUIT (HIGH TEMPERATURE INDICATED) 1993

The transmission fluid temperature sensor is a thermistor which controls the signal voltage to the PCM/TCM. The PCM/TCM applies and monitors voltage on circuit No. 1227 to the sensor. When transmission fluid is cold, sensor resistance is high: therefore, the PCM/TCM will see high signal voltage. As the transmission fluid temperature warms up, sensor resistance and voltage will drop. At normal transmission operating temperature of 212°F (100°C), voltage will be about 1.5-2.0 volts.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) DTC 58 will set if signal voltage indicates a transmission fluid temperature greater than 305°F (151°C) for one second.

Test Number 2) This step determines if circuit No. 1227 is shorted to ground, which will result in conditions for DTC 58.

Check harness routing for a potential short to ground in circuit No. 1227. Scan tool displays transmission fluid temperature in degrees Centigrade. After transmission has been in operation, temperature should rise steadily to about 212°F (100°C) then stabilize. Test transmission sensor at various temperature levels to determine if sensor is out of calibration. See TRANSMISSION SENSOR - TEMP TO RESISTANCE chart. An out-of-calibration sensor could result in delayed shifts or TCC enabled complaint.

Scheme 113

Scheme 114

DTC 58, TRANSMISSION FLUID TEMPERATURE SENSOR CIRCUIT (HIGH TEMPERATURE INDICATED) 1994

The transmission fluid temperature sensor is a thermistor which controls the signal voltage to the PCM/TCM. The PCM/TCM supplies a 5 volt reference signal to the sensor on circuit No. 1227. When transmission fluid is cold, sensor resistance is high and PCM/TCM will sense high signal voltage. As transmission fluid temperature warms to normal operating temperature of 212°F (100°C), sensor resistance becomes less and voltage decreases to about 1.5 to 2 volts. With a DTC 79 also set, check transmission cooling system. DTC 58 will set when signal voltage indicates fluid temperature greater than 306°F (151°C) for one second. PCM/TCM will default to warm fluid temperature value.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This test checks for short to ground or faulty sensor.

Test Number 2) This test checks for an internal fault within transmission by creating an open.

Check harness routing for potential short to ground in circuit No. 1227. Scan tool displayed temperature should rise steadily to about 212°F (100°C), then stabilize. Test transmission sensor at various temperature levels to determine if sensor is out of calibration. See TEMPERATURE-TO-RESISTANCE VALUES (DTC 58) table. An out-of-calibration sensor could result in firm shifts or TCC enable complaint.

TEMPERATURE-TO-RESISTANCE VALUES (1) (DTC 58)

Scheme 115

Scheme 116

DTC 59, TRANSMISSION FLUID TEMPERATURE SENSOR CIRCUIT (LOW TEMPERATURE INDICATED) 1993

The transmission fluid temperature sensor is a thermistor which controls the signal voltage to the PCM/TCM. The PCM/TCM applies and monitors voltage on circuit No. 1227 to the sensor. When transmission fluid is cold, sensor resistance is high: therefore, the PCM/TCM will see high signal voltage. As the transmission fluid temperature warms up, sensor resistance and voltage will drop. At normal transmission operating temperature of 212°F (100°C), voltage will be about 1.5-2.0 volts.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) DTC 59 will set if signal voltage indicates a transmission fluid temperature less than -34°F (-37°C) for one second.

Test Number 2) This test simulates conditions for DTC 58. If PCM/TCM recognizes low voltage signal, scan tool will display temperature greater than 304°F (151°C), indicating control module and wiring are not at fault.

Test Number 3) This test determines if circuit No. 1227 is open. There should be 5 volts present at transmission sensor connector.

Scan tool displays transmission fluid temperature in degrees Centigrade. After transmission has been in operation, temperature should rise steadily to about 212°F (100°C) then stabilize. A faulty connection or an open in circuit No. 455/452 or circuit No. 1227 will result in a DTC 59. Test transmission sensor at various temperature levels to determine if sensor is out of calibration. See TRANSMISSION SENSOR - TEMP TO RESISTANCE chart. An out-of-calibration sensor could result in firm shifts or TCC enabled complaint.

Scheme 117

DTC 59, TRANSMISSION FLUID TEMPERATURE SENSOR CIRCUIT (LOW TEMPERATURE INDICATED) 1994

The transmission fluid temperature sensor is a thermistor which controls the signal voltage to the PCM/TCM. The PCM/TCM supplies a 5 volt reference signal to the sensor on circuit No. 1227. When transmission fluid is cold, sensor resistance is high and PCM/TCM will sense high signal voltage. As transmission fluid temperature warms to normal operating temperature of 212°F (100°C), sensor resistance becomes less and voltage decreases to about 1.5 to 2 volts. DTC 59 will set when signal voltage indicates fluid temperature less than -40°F (-40°C) for one second. PCM/TCM will default to warm fluid temperature value.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This checks entire circuit and indicates if malfunction is present.

Test Number 2) This test simulates DTC 58. If PCM/TCM recognizes the low signal voltage (high temperature)) and scan tool displays 305°F (151°C) or more, PCM/TCM and wiring are okay.

Test Number 3) This test determines if circuit No. 1227 is open. There should be 5 volts present at sensor connector if measuring with a DVOM.

Scan tool displays transmission fluid temperature in degrees Centigrade. After transmission is operating, displayed temperature should rise steadily to about 212°F (100°C) then stabilize. A poor connection or an open circuits No. 455/1227 will result in DTC 59. Test transmission sensor at various temperature levels to determine if sensor is out of calibration. See TEMPERATURE-TO-RESISTANCE VALUES (DTC 59) table. An out-of-calibration sensor could result in firm shifts or TCC enable complaint.

TEMPERATURE-TO-RESISTANCE VALUES (1) (DTC 59)

Scheme 118

Scheme 119

DTC 63 & 64, BAROMETRIC PRESSURE SENSOR CIRCUIT HIGH OR LOW (1994) DIESEL

The TCM supplies 5 volts to the barometric pressure sensor. As the atmospheric pressure changes, the resistance within the sensor also changes, modifying the voltage on the sensor input signal. When atmospheric pressure is high, input signal voltage will also be high (about 4.5 volts). As atmospheric pressure decreases, input signal voltage decreases.

DTC 63 will set when sensor signal voltage is greater than 4.9 volts for greater than 2 seconds. DTC 64 will set when sensor signal voltage is less than 1.9 volts for greater than 2 seconds.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This verifies the 5 volt supply to barometric pressure sensor.

Test Number 2) If entire circuit is okay, voltage measured will be 5 volts.

If DTC will not set, use snapshot mode on scan tool to set DTC, then review data to identify malfunction.

Scheme 120

Scheme 121

DTC 68, OVERDRIVE RATIO ERROR (1993)

The PCM/TCM monitors the difference in engine RPM and input shaft RPM. With transmission in Drive, scan tool reading should show engine speed closely matching input speed.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) DTC 68 will set under following conditions: engine speed is 200 RPM greater than input speed, 4th gear is indicated, TCC is enabled, and all conditions are met for 2 seconds.

Test Number 2) This step checks transmission signal being sent to PCM/TCM.

Test Number 3) This step checks for engine RPM signal being sent to PCM/TCM.

Check transmission pass-through connector. DTC 68 will set if transmission defaults to 2nd gear. If problems are still present, check for possible internal transmission problems.

Scheme 122

Scheme 123

DTC 68, OVERDRIVE RATIO ERROR (1994)

The PCM/TCM monitors the difference in engine RPM and input shaft RPM. With transmission in Drive, scan tool reading should show engine speed closely matching input speed. DTC 68 will set when DTC(s) 28, 71 or 74 is not present, TCC slip speed is greater than 200 RPM, 4th gear is indicated, TCC is locked, vehicle is not in Park or Neutral and all conditions are met for 2 seconds. PCM/TCM will inhibit TCC operation.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This test checks indicated range to actual selected range. A faulty switch could set DTC 68.

Test Number 2) This test checks torque converter for slippage while in a commanded lock-up state.

Check for deformed connections at pass-thru connector. DTC 68 will set when transmission defaults to 2nd gear. An intermittent incorrect engine speed signal will set DTC 68 if incorrect signal lasts for greater than 2 seconds. A mechanical failure in solenoid "A" (1-2 shift solenoid stuck off) or solenoid "B" (2-3 shift solenoid stuck on) could set DTC 68.

Scheme 124

Scheme 125

DTC 69, TORQUE CONVERTER CLUTCH (TCC) STUCK ON (1994)

The purpose of the automatic transmission Torque Converter Clutch (TCC) feature is to eliminate power loss of the torque converter stage when vehicle is in a cruise condition. This allows the convenience of the automatic transmission, and fuel economy of a manual transmission.

PCM/TCM commands the TCC PWM solenoid on by modulating TCC signal fluid acting on converter clutch shift valve. TCC fluid applies torque converter clutch.

DTC 69 will set when DTC(s) 21, 22, 28, 71 or 74 is not present, TCC is commanded off, TCC slip speed is between -5 and 10 RPM, TPS signal is greater than 25 percent, transmission range switch indicates "D3" or "D4", transmission is in 2nd or 3rd gear and all conditions are met for 2 seconds.

Note. Test number refers to number on diagnostic chart.

Test Number 1) This test checks mechanical state of TCC. When PCM/TCM commands TCC solenoid off, TCC slip speed should increase.

If TCC is mechanically stuck on, vehicle speed is zero, brakes are applied and "D2" is selected, TCC fluid will mechanically apply TCC, causing engine to stall.

Scheme 126

DTC 71, CAMSHAFT POSITION SENSOR CIRCUIT LOW (1994) DIESEL

The Camshaft Position (CMP) sensor detects the rotational speed of the camshaft. As the camshaft rotates, an A/C signal is generated in the circuit. This signal provides the input to determine engine speed for use in various calculations including TCC slip speed and overdrive ratio. DTC 71 will set when DTC 28 is not present, engine speed is less than 50 RPM, transmission range switch indicates "D4", "D3", "D1" or Reverse and conditions are met for 2 seconds. TCM will inhibit TCC.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) An out-of-range transmission fluid pressure switch could falsely indicate the actual transmission range.

Test Number 2) This checks the entire CMP sensor circuit for proper signal.

Test Number 3) A signal at this point indicates that the sensor is capable of inducing an AC voltage in the circuit.

A mechanical problem with the camshaft may set DTC 71. With CMP sensor removed, check camshaft for damage.

Scheme 127

Scheme 128

DTC 73, FORCE MOTOR CURRENT (CURRENT ERROR) 1993

Force motor, also referred to as pressure control solenoid, is aPCM/TCM-controlled device used to regulate transmission line pressure. The PCM/TCM looks at TPS voltage, engine RPM and other inputs to determine appropriate line pressure for a given load, then regulates the pressure by applying a varying amperage. The applied amperage can vary from 1 to 1.1 amps.

The PCM/TCM then monitors amperage at the return line. If the return amperage varies more than .16 amp from the commanded amperage for the duration of at least one second, DTC 73 will set. Once DTC 73 is set, the force motor is disabled and maximum line pressure will be applied until the next time the ignition switch is cycled. DTC 73 will remain stored, but the force motor will resume normal function until the conditions for DTC 73 re-occur.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This step checks control of force motor by PCM/TCM.

Test Number 2) Voltage should be present.

Test Number 3) This step checks for low resistance inside transmission.

Test Number 4) This step checks for short to ground.

Test Number 5) This step checks for high resistance inside transmission.

Check transmission pass-through connector and PCM/TCM for poor connections.

Scheme 129

Scheme 130

DTC 73, FORCE MOTOR CURRENT (CURRENT ERROR) 1994

Force motor, also referred to as pressure control solenoid, is a PCM/TCM controlled device used to regulate transmission line pressure. PCM/TCM looks at TPS voltage, engine RPM and other inputs to determine the appropriate line pressure for a given load, then regulates the pressure by applying a variable amperage to the pressure control solenoid. Applied amperage varies from .1 to 1.1 amps.

PCM/TCM monitors amperage at the return line. DTC 73 will set if the return line amperage varies greater than .16 amp from the commanded amperage for at least one second, and DTC 75 is not present. When DTC 73 sets, maximum line pressure will be applied, causing harsh shifts until the next ignition cycle.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This test checks ability of PCM/TCM to command pressure control solenoid.

Test Number 2) This test checks internal transmission harness and pressure control solenoid for high resistance.

Check for poor connection at all connections, especially those at the transmission pass-thru connector and PCM/TCM.

Scheme 131

Scheme 132

Scheme 133

DTC 74, INPUT SPEED SENSOR CIRCUIT (1994)

Transmission input speed sensor consists of a permanent magnet surrounded by a coil of wire. As the forward clutch housing rotates, an A/C voltage is induced in the circuit. Signal voltage and frequency vary directly with the forward clutch rotational speed.

DTC 74 will set when DTC(s) 24, 28 or 71 is not present, transmission is not in Park or Neutral, engine speed is greater than 300 RPM, output speed is greater than 200 RPM, input speed is less than 50 RPM and all conditions are met for 2 seconds. PCM/TCM will inhibit TCC operation.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This test checks entire circuit for continuity.

Test Number 2) This test checks output of input speed sensor.

Check for poor connection at all connections, especially those at the transmission pass-thru connector and PCM/TCM.

Scheme 134

Scheme 135

Scheme 136

DTC 75, SYSTEM VOLTAGE LOW (1993)

DTC 75 will set when ignition is on and PCM/TCM 12-volt battery feed voltage is less than 8.6 volts for about 4 seconds. During the time failure is present, force motor, also referred to as pressure control solenoid, is turned off, maintaining only 2nd gear, and inhibiting TCC operation.

Note. Test numbers refer to test numbers on diagnostic chart.

Test Number 1) Normal system charging voltage is 9-15 volts.

Test Number 2) This step checks if low voltage reading is due to alternator, circuit No. 440 or PCM/TCM. With engine running, check voltage at battery. If voltage is less than 8.6 volts, PCM/TCM is okay.

Intermittents

If code sets when an accessory is operated, check for poor connections or excessive current draw. Also, check for poor connections at starter solenoid or fusible link. Minimum voltage allowed for DTC 75 to set is on a graduated scale and changes with temperature. Minimum voltage at -40°F (-40°C) is 6.7 volts. Minimum voltage at 194°F (90°C) is 8.6 volts. Minimum voltage at 304°F (150°C) is 10.5 volts.

Scheme 137

Scheme 138

DTC 75, SYSTEM VOLTAGE LOW (1994)

Ignition voltage is supplied to PCM/TCM to indicate ignition switch status. Battery voltage is supplied to PCM/TCM to maintain memory of learned functions and parameters. DTC 75 will set when ignition is on and engine speed is greater than 1000 RPM for 4 seconds. PCM/TCM will default to maximum line pressure, shift transmission to 2nd gear, and inhibit TCC and 4th gear.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) Normal battery voltage is 9-15 volts.

Test Number 2) This test checks if alternator is faulty under load conditions. With engine running, check voltage at battery. If voltage is more than 15 volts, repair malfunction in charging system.

Jump-starting engine and charging battery may set DTC 52 or DTC 53. If DTC(s) set when accessory is operated, check for poor connections or excessive current draw. Also check for poor connections at starter solenoid and fusible link. Minimum voltage allowed for DTC 75 to set is on a graduated scale and changes with temperature. Minimum voltage at -40°F (-40°C) is 7.3 volts. Minimum voltage at 194°F (90°C) is 10.3 volts. Minimum voltage at 304°F (150°C) is 11.7 volts.

Scheme 139

Scheme 140

DTC 79, TRANSMISSION FLUID TEMPERATURE SENSOR CIRCUIT (HIGH TEMPERATURE INDICATED) 1994

The transmission fluid temperature sensor is a thermistor which controls the signal voltage to the PCM/TCM. The PCM/TCM supplies a 5 volt reference signal to the sensor on circuit No. 1227. When transmission fluid is cold, sensor resistance is high and PCM/TCM will sense high signal voltage. As transmission fluid temperature warms to normal operating temperature of 212°F (100°C), sensor resistance becomes less and voltage decreases to approximately 1.5 to 2 volts. DTC 79 will set when DTC 58 is not present and signal voltage indicates temperature greater than 295°F (146°C) for 30 seconds.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This test checks for short to ground or faulty sensor.

Test Number 2) This test simulates DTC 59.

Check harness routing for potential short to ground in circuit No. 1227. Scan tool displayed temperature should rise steadily to about 212°F (100°C), then stabilize. Test transmission sensor at various temperature levels to determine if sensor is out of calibration. See TEMPERATURE-TO-RESISTANCE VALUES (DTC 79) table. An out-of-calibration sensor could result in firm shifts or TCC enable complaint.

TEMPERATURE-TO-RESISTANCE VALUES (1) (DTC 79)

Scheme 141

Scheme 142

DTC 81, SOLENOID "B" CIRCUIT FAULT (1993)

The PCM/TCM continually monitors voltage on each circuit connected to the quad-driver, looking for either low or high voltage, depending on the commanded state of the devices connected to it. DTC 81 will set if a fault has been detected on the shift solenoid "B" circuit, also referred to as 2-3 shift solenoid. For example, if shift solenoid "B" is commanded on by the PCM/TCM, voltage on that circuit should drop when solenoid is grounded. If voltage remains high for at least 2 seconds, DTC 81 will set. The opposite is also true. If shift solenoid "B" is off, voltage on the circuit should remain high. If voltage drops for greater than 2 seconds, DTC 81 will set.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This step checks shift solenoid "B" and circuits inside transmission for shorts.

Test Number 2) Battery voltage should be present at shift solenoid "B".

Test Number 3) This step checks circuit No. 1223 for short to ground.

Test Number 4) This step checks if PCM/TCM can control solenoid "B". If bidirectional scan tool is not available, solenoid may be activated by grounding ALDL test terminal "B" with ignition on and engine off.

Test Number 5) This determines whether circuit No. 1223 is open or PCM/TCM is faulty.

Check transmission pass-through connector and PCM/TCM for poor connections.

Scheme 143

Scheme 144

DTC 81, SOLENOID "B" CIRCUIT FAULT (1994)

The PCM/TCM continually monitors voltage on each circuit connected to the quad-driver, looking for either low or high voltage, depending on the commanded state of the devices connected to it. DTC 81 will set if a fault has been detected on the shift solenoid "B" circuit, also referred to as 2-3 shift solenoid. For example, if shift solenoid "B" is commanded on by the PCM/TCM, voltage on that circuit should drop when solenoid is grounded. If voltage stays up for at least 2 seconds, DTC 81 will set. The opposite is also true. If shift solenoid "B" is off, voltage on the circuit should remain high. If voltage drops for more than 2 seconds, DTC 81 will set. PCM/TCM will default to maximum line pressure, 2nd or 3rd gear operation only and no TCC.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This test checks function of shift solenoid "B" and transmission internal wiring.

Test Number 2) This test checks for power to shift solenoid "B" from ignition through the fuse.

Check all connections, especially at transmission pass-thru connector. An open in the ignition feed circuit may cause multiple DTC's to set.

Scheme 145

Scheme 146

Scheme 147

DTC 82, SOLENOID "A" CIRCUIT FAULT (1993)

The PCM/TCM continually monitors voltage on each circuit connected to the quad-driver, looking for either low or high voltage, depending on the commanded state of the devices connected to it. DTC 82 will set if a fault has been detected on the shift solenoid "A" circuit, also referred to as 1-2 shift solenoid. For example, if shift solenoid "A" is commanded on by the PCM/TCM, voltage on that circuit should drop when solenoid is grounded. If voltage remains high for at least 2 seconds, DTC 82 will set. The opposite is also true. If shift solenoid "A" is off, voltage on the circuit should remain high. If voltage drops for more than .5 second or longer, DTC 82 will set.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This step checks shift solenoid "A" and circuits inside transmission for shorts.

Test Number 2) Battery voltage should be present at shift solenoid "A".

Test Number 3) This step checks circuit No. 1222 for short to ground.

Test Number 4) This step checks if PCM/TCM can control solenoid "A". If bidirectional scan tool is not available, solenoid may be activated by grounding ALDL test terminal "B" with ignition on and engine off.

Check transmission pass-through connector and PCM/TCM for poor connections.

Scheme 148

Scheme 149

DTC 82, SOLENOID "A" CIRCUIT FAULT (1994)

The PCM/TCM continually monitors voltage on each circuit connected to the quad-driver, looking for either low or high voltage, depending on the commanded state of the devices connected to it. DTC 82 will set if a fault has been detected on the shift solenoid "A" circuit, also referred to as 1-2 shift solenoid. For example, if shift solenoid "A" is commanded on by the PCM/TCM, voltage on that circuit should drop when solenoid is grounded. If voltage stays up for at least 2 seconds, DTC 82 will set. The opposite is also true. If shift solenoid "A" is off, voltage on the circuit should remain high. If voltage drops for greater than 2 seconds, DTC 82 will set. PCM/TCM will default to maximum line pressure, 2nd or 3rd gear operation, or 1st and 4th gear operation only.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This test checks function of shift solenoid "A" and transmission internal wiring.

Test Number 2) This test checks for power to shift solenoid "A" from ignition through the fuse.

Check all connections, especially at transmission pass-thru connector. An open in the ignition feed circuit may cause multiple DTC's to set.

Scheme 150

Scheme 151

Scheme 152

DTC 83, TCC SOLENOID CIRCUIT FAULT (1993)

PCM/TCM continually monitors voltage on each circuit connected to the quad-driver for either low or high voltage, depending on the commanded state of the device connected to it. DTC 83 will set ifPCM/TCM detects an inappropriate reading on the TCC circuit. For example, if the TCC duty cycle is zero, but voltage on the TCC circuit drops as if the solenoid were on, the DTC 83 will set. The TCC solenoid, because of its large current draw, is connected to 2 terminals of a single quad-driver.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This tests for low resistance in the solenoid or internal transmission harness. Test also determines which circuit triggered fault. If bidirectional scan tool is not available, TCC may be activated by grounding ALDL test terminal "B" with ignition on and engine off.

Test Number 2) Battery voltage should be present at TCC solenoid.

Test Number 3) This step checks circuit No. 422 for short to ground.

Test Number 4) This step checks if PCM/TCM can control TCC solenoid.

Check transmission pass-through connector and PCM/TCM for poor connections.

Scheme 153

Scheme 154

Scheme 155

DTC 83, TCC SOLENOID CIRCUIT FAULT (1994)

The PCM/TCM supplies a ground through an internal quad-driver module, allowing current to flow through the solenoid coil according to the duty cycle (percentage of on and off time). This current flow through the solenoid coil creates a magnetic field that magnetizes the solenoid core. The magnetized core attracts the check ball to seat against spring pressure. This blocks the exhaust for the TCC signal fluid and allows 2-3 drive fluid to feed the TCC signal circuit. The TCC signal fluid pressure acts on the TCC regulator valve to regulate line pressure and to apply fluid pressure to the TCC shift valve. When the TCC shift valve is in the apply position, regulated apply fluid pressure is directed through the TCC valve to apply the torque converter clutch.

The PCM/TCM continually monitors voltage on each circuit connection to the quad-driver for either low or high voltage, depending on the commanded state of the device connected to it. DTC 83 will set if PCM/TCM commands the solenoid on and voltage remains high (battery voltage), or PCM/TCM commands solenoid off and voltage remains low (zero volts). Condition must be met for 2 seconds. PCM/TCM will default to inhibit TCC operation and 4th gear operation if in hot mode.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This test checks if PCM/TCM is commanding the TCC solenoid on.

Test Number 2) This test will check for voltage to the solenoid.

Check all connections, especially those at the transmission pass-thru connector.

Scheme 156

Scheme 157

Scheme 158

DTC 85, UNDEFINED GEAR RATIO (1993)

While in each gear, PCM/TCM calculates actual gear ratio from input and output speed readings, also referred to as vehicle speed, then compares these to what gear ratio should be, taking into consideration selected gear range. This monitor includes reverse gear, but does not include overdrive gear.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This step checks operation of input sensor.

Test Number 2) This step checks operation of output sensor.

The PCM/TCM relies on Vehicle Speed Sensor Buffer Module (DRAC) to indicate what gear range has been selected. DRAC must be functioning properly or DTC 85 may be set. Check all connections, especially those at the transmission pass-thru connector. Compare scan tool gear ratio reading to specifications in GEAR RATIO table.

GEAR RATIO

Scheme 159

Scheme 160

DTC 85, UNDEFINED GEAR RATIO (1994)

While in each gear, PCM/TCM calculates actual gear ratio from input and output speed sensor readings, also referred to as the vehicle speed, then compares these to what gear ratio should be, taking into consideration selected gear range. This monitor includes reverse gear, but does not include overdrive gear.

DTC 85 will set when DTC(s) 21, 22, 24, 28, 71, 72 or 87 is not present, throttle position is greater than 25 percent, transmission is not in Park, Neutral or 4th gear, engine speed is greater than 300 RPM and vehicle speed is greater than 7 MPH. All conditions must be met for 2 seconds.PCM/TCM will default to maximum line pressure and inhibit TCC operation.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) An out-of-range transmission fluid pressure switch could falsely indicate the actual transmission range.

Test Number 2) This test checks the calculated ratio to determine if the ratio is within parameters.

DTC 85 will set when an unknown gear ratio is detected for any gear except 4th gear. See GEAR RATIO table for commanded gear and ratio range.

GEAR RATIO

Scheme 161

Scheme 162

Scheme 163

DTC 86, LOW GEAR RATIO (1993)

Shift solenoids are used inside valve body to control spool valves, which determine the transmission gear. Fused ignition power is supplied to solenoid "B", also referred to as 2-3 shift solenoid. PCM/TCM engages solenoid "B" by grounding circuit No. 1223. DTC 86 will set under following conditions: vehicle speed is greater than 7 MPH, TPS value is greater than 25 percent of total TPS travel, 1st or 2nd gear operation is requested by PCM/TCM, and transmission ratio indicates 3rd or 4th gear. All conditions must be met for 6 seconds.

Note. Test number refers to number on diagnostic chart.

Test Number 1) This step checks if PCM/TCM can control solenoid "B".

Check transmission pass-through connector. If problems are still present, check for possible internal transmission problems.

Scheme 164

DTC 86, LOW GEAR RATIO (1994)

While in each gear, PCM/TCM calculates actual gear ratio from input and output speed sensor readings, also referred to as the vehicle speed, then compares these to what gear ratio should be, taking into consideration selected gear range.

DTC 86 will set when DTC(s) 21, 22, 24, 28, 71, 72 or 74 is not present, throttle position is greater than 25 percent, transmission is not in Park, Neutral or Reverse, engine speed is greater than 300 RPM, vehicle speed is greater than 7 MPH and transmission gear ratio is less than 1.06 in 1st or 2nd gear. All conditions must be met for 2 seconds.PCM/TCM will default to maximum line pressure, 2nd gear and inhibit TCC operation.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) An out-of-range transmission fluid pressure switch could falsely indicate the actual transmission range.

Test Number 2) This test compares the known ratio for a commanded gear to the calculated ratio displayed on the scan tool.

DTC 86 will set when transmission commanded gear is 1st or 2nd and transmission is mechanically in 3rd or 4th gear. DTC 81 is used to detect a solenoid "B" (2-3 shift solenoid) circuit malfunction.

Scheme 165

DTC 87, HIGH GEAR RATIO (1993)

Shift solenoids are used inside valve body to control spool valves, which determine the transmission gear. Fused ignition power is supplied to solenoid "B", also referred to as 2-3 shift solenoid. PCM/TCM engages solenoid "B" by grounding circuit No. 1223. DTC 87 will set under following conditions: vehicle speed is greater than 7 MPH, TPS value is greater than 25 percent of total TPS travel, 3rd or 4th gear operation is requested by PCM/TCM, and transmission ratio indicates 1st or 2nd gear. All conditions must be met for 6 seconds.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This step checks if PCM/TCM can control solenoid "B". If bidirectional scan tool is not available, solenoid may be activated by grounding ALDL test terminal "B" with ignition on and engine off.

Test Number 2) Battery supply should be present at PCM/TCM.

Test Number 3) This step checks shift solenoid "B" and circuits inside transmission for shorts.

Check transmission pass-through connector. If problems are still present, check for possible internal transmission problems.

Scheme 166

DTC 87, HIGH GEAR RATIO (1994)

While in each gear, PCM/TCM calculates actual gear ratio from input and output speed sensor readings, also referred to as the vehicle speed, then compares these to what gear ratio should be, taking into consideration selected gear range.

DTC 87 will set when DTC(s) 21, 22, 24, 28, 71, 72 or 74 is not present, throttle position is greater than 25 percent, transmission is not in Park, Neutral or Reverse, engine speed is greater than 300 RPM, transmission fluid temperature is greater than (20°C), vehicle speed is greater than 7 MPH and transmission gear ratio is greater than 1.42 in 3rd or 4th gear. All conditions must be met for 2 seconds. PCM/TCM will default to maximum line pressure, 2nd gear and inhibit TCC operation.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) An out-of-range transmission fluid pressure switch could falsely indicate the actual transmission range.

Test Number 2) This test compares the known ratio for a commanded gear to the calculated ratio displayed on the scan tool.

DTC 87 will set when transmission commanded gear is 3rd or 4th and transmission is mechanically in 1st or 2nd gear. DTC 81 is used to detect a solenoid "B" (2-3 shift solenoid) circuit malfunction.

Scheme 167

COMPONENT TEST CHARTS (NO CODES)

Note. If self-diagnostics are not used, following charts may help diagnose electronic transmission controls.

TCC TESTING

Note. When diagnosing converter clutch problems, ensure engine and vacuum systems are operating properly. For torque converter clutch electrical circuit information, see WIRING DIAGRAMS.

Converter Clutch Solenoid

Disconnect harness connector to Torque Converter Clutch (TCC) solenoid. Measure resistance between TCC solenoid terminals. Solenoid resistance should be greater than 20 ohms. (Scheme 168)

Note. Some solenoids have an internal pressure switch in series with the solenoid winding and will not show continuity until that pressure switch is applied by transmission hydraulic pressure.

Converter Lock-Up Signal At Transmission

1. Warm engine to operating temperature. Raise vehicle and support suspension where necessary to prevent damage to drive axles.
2. Disconnect converter clutch connector at transmission. Connect a test light across converter clutch harness terminals. Start engine and place transmission in Drive. Accelerate vehicle to 45 MPH and note test light.
3. If test light is not on, check solenoid power supply wire of harness for open or short to ground. Check ground circuit for open between harness connector and PCM. If harness is okay, see CONVERTER LOCK-UP SIGNAL FROM PCM.

Converter Lock-Up Signal From PCM

1. Warm engine to operating temperature. Raise vehicle and support suspension where necessary to prevent damage to drive axles.
2. Connect a test light to battery voltage. Touch TCC control driver terminal with test light. (Scheme 168) Accelerate vehicle to 45 MPH and note test light. If test light does not illuminate, problem is a faulty PCM connector or PCM.

Torque Converter Clutch Schematic (Typical). Scheme 168

VEHICLE SPEED SENSOR CHECK

The Vehicle Speed Sensor (VSS) circuit consists of a magnetic induction-type sensor, VSS buffer module (also referred to as the DRAC) and wiring. Gear teeth, pressed on outside diameter of output carrier assembly, induce an alternating current in sensor.

This current is transmitted to the buffer module, where it is passed on to the PCM/TCM. The buffer module compensates for various axle ratios, and converts the signal to a square wave for use by the speedometer, cruise control and anti-lock brake system.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This test checks the VSS signal to the PCM/TCM.

Test Number 2) This test checks the VSS signal to the buffer module.

Test Number 3) This test checks VSS signal.

Check all connections, especially at transmission pass-thru connector. If the input sensor is not operational at start up, it can cause the VSS to read zero. While DTC 24 is set, scan tool will display RPM derived from input speed.

Scheme 169

Scheme 170

Scheme 171

Scheme 172

INPUT SPEED SENSOR CIRCUIT (1993)

The input speed sensor is of the magnetic induction type and is located on the left side of the transmission, forward of center. Serrations in the forward clutch housing induce a small A/C current as they pass by the input speed sensor. While there is no specific code for an input speed sensor problem, the PCM/TCM uses input speed sensor readings to calculate gear ratio, turbine speed and TCC slip, and determine if engine is running.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This test checks input sensor circuit to PCM/TCM.

Test Number 2) This test checks input speed sensor output.

Check transmission pass-through connector and PCM/TCM for poor connections.

Scheme 173

Scheme 174

BRAKE SIGNAL CIRCUIT (1993)

The normally closed brake switch supplies a 12-volt signal on circuit No. 420 to the PCM/TCM. The signal voltage is removed when brakes are applied. An incorrect brake signal may affect TCC operation.

Note. Test numbers refer to numbers on diagnostic chart. Display may vary depending on manufacturer of scan tool. Display may read APPLIED, RELEASED, ON or OFF.

Test Number 1) This test checks for voltage at brake switch.

Test Number 2) This test simulates closed brake switch (brakes off).

Test Number 3) This test checks circuit No. 420 from brake switch to PCM/TCM.

Test Number 4) This test opens circuit No. 420 and simulates condition of brakes being applied.

Check for problem with one or more of following components: fuse, power supply circuit, brake switch or wire before splice. Check for wire or circuit problem between splice and PCM/TCM, poor connection to PCM/TCM or faulty PCM/TCM.

Scheme 175

Scheme 176

PRESSURE SWITCH MANIFOLD CIRCUIT CHECK (1993-94)

A fault in the Pressure Switch Manifold (PSM) circuit, also referred to as fluid pressure switch assembly circuit, should result in the setting of a related trouble code. If a problem is suspected with this circuit and a code is not set, go to DTC 28, PRESSURE SWITCH MANIFOLD FAULT chart.

TORQUE CONVERTER CLUTCH (TCC) CIRCUIT CHECK (1993)

The automatic transmission TCC eliminates power loss of torque converter stage when vehicle is in a cruise condition. This allows the convenience of an automatic transmission and fuel economy of a manual transmission.

Fused battery ignition is supplied to TCC solenoid, located inside valve body, to shift a spool valve in order to modulate pressure to TCC. PCM/TCM engages TCC by grounding circuit No. 422 to energize solenoid.

TCC will engage under following conditions: vehicle speed is greater than 30 MPH, transmission is in 4th gear, engine and transmission are at normal operation temperatures, brake switch is closed, throttle position switch signal is steady, and no codes are stored.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This test checks TCC solenoid and circuits inside transmission for shorts.

Test Number 2) This test verifies power supply to TCC solenoid.

Test Number 3) This test checks for short to ground in circuit No. 422.

Test Number 4) This test checks for PCM/TCM control of TCC. If bidirectional scan tool is not available, TCC may be activated by grounding ALDL test terminal "B" with ignition on and engine off.

Check transmission pass-through connector and PCM/TCM for poor connections. TCC solenoid is pulse width modulated (frequency controlled) and will allow some slight slippage.

Scheme 177

SHIFT SOLENOID "A" CIRCUIT CHECK (1993)

Shift solenoid "A", also referred to as 1-2 shift solenoid, is attached to the valve body and is a normally open exhaust valve. The PCM/TCM activates the solenoid by grounding it through an internal quad-driver. Solenoid "A" (Gray) is on in 1st and 4th gears, but is off in 2nd and 3rd gears. When solenoid is on, it redirects fluid to act on the shift valves.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This test checks shift solenoid "A" and circuits inside transmission for shorts.

Test Number 2) Battery voltage should be present at shift solenoid "A".

Test Number 3) This test checks circuit No. 1222 for short to ground.

Test Number 4) This test checks if PCM/TCM can control solenoid "A". If bidirectional scan tool is not available, solenoid may be activated by grounding ALDL test terminal "B" with ignition on and engine off.

Check transmission pass-through connector and PCM/TCM for poor connections.

Scheme 178

SHIFT SOLENOID "B" CIRCUIT CHECK (1993)

Shift solenoid "B", also referred to as 2-3 shift solenoid, is attached to the valve body and is a normally open exhaust valve, which determines the transmission gear. Solenoid "B" (Green) is on in 3rd and 4th gears, but is off in 1st and 2nd gears. Fused ignition voltage is supplied to solenoid "B". PCM/TCM engages solenoid "B" by grounding circuit No. 1223.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This test checks shift solenoid "B" and circuits inside transmission for shorts.

Test Number 2) Battery voltage should be present at shift solenoid "B".

Test Number 3) This test checks circuit No. 1223 for short to ground.

Test Number 4) This test checks if PCM/TCM can control solenoid "B". If bidirectional scan tool is not available, solenoid may be activated by grounding ALDL test terminal "B" with ignition on and engine off.

Test Number 5) This determines whether circuit No. 1223 is open or PCM/TCM is faulty.

Check transmission pass-through connector and PCM/TCM for poor connections.

Scheme 179

FORCE MOTOR CIRCUIT CHECK (1993)

The force motor, also referred to as pressure control solenoid, is aPCM/TCM-controlled device used to regulate transmission line pressure. PCM/TCM looks at TPS voltage, engine RPM, and other inputs to determine appropriate line pressure for a given load, then regulates pressure by applying a variable amperage to the force motor. Applied amperage varies from .1 to 1.1 amps.

Note. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This test checks control of force motor by PCM/TCM.

Test Number 2) Voltage should be present.

Test Number 3) This test checks for low resistance inside transmission.

Test Number 4) This test checks for short to ground.

Test Number 5) This test checks for high resistance inside transmission.

Check transmission pass-through connector and PCM/TCM for poor connections.

Scheme 180

4WD LOW SWITCH SIGNAL CHECK (1994)

The 4WD low circuit consists of a transfer case switch, front axle actuator and wiring. The PCM/TCM supplies a battery voltage signal to the transfer case switch on circuit No. 1493. With 2WD or 4WD HI selected, no ground path is provided for circuit No. 1493, and voltage signal at PCM/TCM will be battery voltage. When 4WD low is selected, transfer case switch provides a ground for circuit No. 1493, andPCM/TCM 4WD low signal will change from battery voltage to zero volts. Transfer case switch also completes circuit No. 50 to circuit No. 1296 to provide battery voltage to front axle actuator. Failure of 4WD low circuit may cause early or late shifts, or erratic shifts.

Note. On diesel models, PCM terminal is E2. Test numbers refer to numbers on diagnostic chart.

Test Number 1) This test checks for proper circuit operation.

Test Number 2) This test checks for proper reference signal from PCM/TCM.

Test Number 3) This test checks the ability of transfer case switch to ground the reference signal from PCM/TCM.

Intermittent problem may be caused by poor electrical connections. Check for poor connections at transfer case switch and PCM/TCM. If connections are okay, see appropriate TRANSFER CASE article.

Scheme 181

Scheme 182

4L80-E Wiring Diagram (1993 "C" & "K" Series - Diesel). Scheme 183

4L80-E Wiring Diagram (1993 "C" & "K" Series - Gasoline). Scheme 184

4L80-E Wiring Diagram (1994 "C" & "K" Series - Diesel). Scheme 185

4L80-E Wiring Diagram (1994 "C" & "K" Series - Gasoline). Scheme 186

4L80-E Wiring Diagram (1993 "G" Series - Diesel). Scheme 187

4L80-E Wiring Diagram (1993 "G" Series - Gasoline). Scheme 188

4L80-E Wiring Diagram (1994 "G" Series - Diesel). Scheme 189

4L80-E Wiring Diagram (1994 "G" Series - Gasoline). Scheme 190

4L80-E Wiring Diagram (1993 "P" Series - Diesel). Scheme 191

4L80-E Wiring Diagram (1993 "P" Series - Gasoline). Scheme 192

4L80-E Wiring Diagram (1994 "P" Series - Diesel). Scheme 193

4L80-E Wiring Diagram (1994 "P" Series - Gasoline). Scheme 194