1988 Jeep Cherokee AUTOMATIC TRANSMISSIONS Aisin Warner 4 Electronic Diagnosis
APPLICATION NOTE: Transmission may also be referred to as AW-4. TRANSMISSION APPLICATION
Vehicle Application Transmission Model Jeep 1987-96 Cherokee ................................... AW4 1987-92 Comanche ................................... AW4 1987 Grand Wagoneer ................................ AW4 1987-90 Wagoneer ................................... AW4 1992 Wrangler ...................................... AW4
NOTE: Vehicle body code may be required when diagnosing or repairing transmission, as body code may be used instead of vehicle model name. See BODY CODE DESIGNATION table. BODY CODE DESIGNATION
Vehicle Model Body Code Cherokee .............................................. XJ Comanche .............................................. MJ Grand Wagoneer ........................................ SJ Wagoneer .............................................. XJ Wrangler .............................................. YJ
DESCRIPTION The electronic control system for the AW-4 transmission controls transmission shift points and torque converter lock-up. Electronic control system consists of Transmission Control Module (TCM), valve body solenoids, throttle position sensor, speed sensor, neutral safety switch and brake switch. NOTE: Transmission Control Module (TCM) may be referred to as Transmission Control Unit (TCU). Neutral safety switch may be referred to as park/neutral safety switch or gear select switch. OPERATION TRANSMISSION CONTROL MODULE (TCM) The TCM determines shift points and torque converter lock-up based on input signals received from throttle position sensor, neutral safety switch, speed sensor and brake switch. The TCM controls transmission shift points and torque converter lock-up by operating electric solenoids mounted on the valve body. The TCM contains a self-diagnostic system used for determining an electronic component failure. The TCM self-diagnostic system will store a diagnostic trouble code in the TCM memory if certain electronic problems exist. If electronic problem goes away, diagnostic trouble code will be erased from TCM memory after ignition has been cycled approximately 75 times. NOTE: Diagnostic trouble code may be referred to as fault code. Diagnostic trouble codes can be retrieved using a Diagnostic Readout Box-II (DRB-II). After repairing an electrical system problem, stored diagnostic trouble code must be cleared from TCM memory. The TCM is located behind right side of instrument panel on Cherokee. See Fig. 1.Fig. 1: Transmission Control Module (TCM) I.D. (Cherokee) Courtesy of Chrysler Corp. VALVE BODY SOLENOIDS Valve body solenoids, mounted on the valve body, are output devices controlled by signals received from the TCM. See Fig. 2. The No. 1 and 2 valve body solenoids control transmission shifts while the No. 3 valve body solenoid is used for torque converter lock-up. When No. 1 and 2 valve body solenoids are energized, solenoid plunger moves from seat. This opens the drain port and releases line pressure. When either valve body solenoid is de energized, plunger closes the drain port. The No. 3 valve body solenoid operates in reverse. When No. 3 valve body solenoid is de-energized, solenoid plunger moves away from seat. This opens the drain port and releases line pressure. When No. 3 valve body solenoid is energized, the plunger closes the drain port. NOTE: For valve body solenoid usage, see VALVE BODY SOLENOID APPLICATION table. VALVE BODY SOLENOID APPLICATION (1)
Shift Lever No. 1 No. 2 Position Solenoid Solenoid "D" (Drive) 1st Gear .................. ON .................... OFF 2nd Gear .................. ON ..................... ON 3rd Gear .................. OFF .................... ON 4th Gear .................. OFF ................... OFF "3" 1st Gear .................. ON .................... OFF 2nd Gear .................. ON ..................... ON 3rd Gear .................. OFF .................... ON "1-2" 1st Gear .................. ON .................... OFF 2nd Gear .................. ON ..................... ON "R" (Reverse) .............. ON .................... OFF "N" Or "P" ................. ON .................... OFF (1) - Valve body contains 3 valve body solenoids. See Fig. 2. No. 1 and 2 valve body solenoids are used for controlling transmission shifts. No. 3 valve body solenoid is used for torque converter lock-up only.
Fig. 2: Identifying Valve Body Solenoids Courtesy of Chrysler Corp. BRAKE SWITCH
Brake switch is an input device mounted above the brake pedal. When brake pedal is operated, brake switch delivers an input signal to the TCM. The TCM uses input signal for controlling No. 3 valve body solenoid for torque converter lock-up. NEUTRAL SAFETY SWITCH NOTE: Neutral safety switch may be referred to as park/neutral safety switch or gear select switch. Neutral safety switch is an input device mounted on the transmission manual valve shaft. Neutral safety switch delivers an input signal to TCM, indicating transmission manual valve gear position. SPEED SENSOR Speed sensor, mounted in adapter housing or extension housing, is an input device consisting of speed sensor rotor and speed sensor. Speed sensor rotor is mounted on transmission output shaft. Input signal is delivered from speed sensor to TCM with each revolution of transmission output shaft. The TCM uses input signal for controlling transmission operation. THROTTLE POSITION SENSOR (TPS) The TPS, mounted on throttle body, determines throttle position and delivers an input signal to TCM. The TCM uses input signal for controlling transmission upshifts and torque converter lock-up. SELF-DIAGNOSTIC SYSTEM DIAGNOSTIC PROCEDURE When performing vehicle diagnosis: * Ensure transmission fluid level is correct and fluid is neither contaminated nor aerated. * Ensure shift cable is properly adjusted. Refer to the appropriate TRANSMISSION SERVICING - A/T article in this section. * Ensure battery is fully charged. * Perform visual inspection, ensuring all electrical connections at transmission, TCM, throttle position sensor, neutral safety switch, speed sensor and brake switch are clean and properly installed. * Perform TEST 1A - VERIFICATION OF THE COMPLAINT under TROUBLE SHOOTING CHARTS in this article. * Repair diagnostic trouble codes in order displayed. * Always perform TEST 2A - VERIFICATION TEST after repair is completed. See TEST 2A - VERIFICATION TEST under TROUBLE SHOOTING CHARTS in this article. RETRIEVING DIAGNOSTIC TROUBLE CODES NOTE: Manufacturer recommends using Chrysler's Diagnostic Readout Box-II (DRB-II) with proper cartridge for system diagnosis. Other after-market scan tools may be used for system diagnosis. The following procedure is for DRB-II scan tool usage. Use manufacturer's instruction for operating the DRB-II scan tool. When retrieving diagnostic trouble codes using DRB-II, you must first enter AW4 MENU and then retrieve diagnostic trouble codes. NOTE: Ensure TEST 1A - VERIFICATION OF THE COMPLAINT is performed when trouble shooting the vehicle. This test checks for diagnostic trouble codes with vehicle stationary and during road test. See TEST 1A - VERIFICATION OF THE COMPLAINT under TROUBLE SHOOTING CHARTS. NOTE: The DRB-II scan tool can be used in several different modes using manufacturer's instructions to activate system components and perform several tests on transmission. See DRB-II OPERATING MODES. Entering AW4 MENU 1) Ensure ignition is off. Connect DRB-II to 6-pin transmission diagnostic connector. See Fig. 3. Transmission diagnostic connector is located to the right of the steering column on driver's side of instrument panel above accelerator pedal or below glove box on passenger's side.Fig. 3: Diagnostic Connector & Terminals I.D. (Cherokee) Courtesy of Chrysler Corp. 2) Turn ignition on. Copyright date and diagnostic program will be briefly displayed. If DRB-II displays an error message, proceed to DRB-II PROBLEMS & ERROR MESSAGES. The following are possible error messages that may appear. * CARTRIDGE ERROR * HIGH BATTERY * KEYPAD TEST FAILURE * LOW BATTERY * RAM TEST FAILURE 3) If no error messages appear, display will read as follows after a few seconds: 1) VEHICLES TESTED, 2) HOW TO USE, 3) CONFIGURE and 4) SELECT SYSTEM. 4) Select 4) SELECT SYSTEM to enter diagnostic system. Once in SELECT SYSTEM, select 2) TRANSMISSION to enter transmission. Display will read 1) EATX and 2) AW4. 5) Select 2) AW4. After a few seconds display will change to read AW4, VERSION 01. After a few seconds, display will read AW4 MENU, 1) SYSTEM TEST and 2) READ FAULTS. If DOWN ARROW is depressed 3 times, display will read as follows: 3) STATE DISPLAY, 4) ACTUATOR TESTS and 5) ADJUSTMENTS. NOTE: The ACTUATOR TESTS and ADJUSTMENTS cannot be used when diagnosing the AW-4 transmission. Retrieving Diagnostic Trouble Codes 1) Select 2) READ FAULTS from AW4 MENU. If no diagnostic trouble code exists, display will read as follows: AW4 FAULTS, NO FAULTS DETECTED. 2) If diagnostic trouble code exists, the following message will be displayed: 1 OF 3 FAULTS. This number will vary depending on number of diagnostic trouble codes stored in the TCM memory. 3) Diagnostic trouble code and message will be displayed. Press DOWN ARROW key to display next diagnostic trouble code. To identify diagnostic trouble code, see DIAGNOSTIC TROUBLE CODE IDENTIFICATION table. NOTE: See TROUBLE SHOOTING CHARTS to diagnose faults indicated by trouble codes. NOTE: Valve body solenoid diagnostic trouble code 700 may appear in a FAULT PRESENT or FAULT STORED status. Status will be displayed along with diagnostic trouble code. Diagnostic trouble code must be diagnosed depending on the status. See TEST 1A - VERIFICATION OF THE COMPLAINT under TROUBLE SHOOTING CHARTS. DIAGNOSTIC TROUBLE CODE IDENTIFICATION
Trouble Code Problem Area 700 (1) .............................. Valve Body Solenoid 702 ......................................... Speed Sensor 703 ............................... (2) Gear Select Switch 705 ............................. Throttle Position Sensor 706 ......................................... Brake Switch 707 ..................................... Wrong TCM Or TCU (1) - Trouble code may apply to individual valve body solenoids. Valve body solenoid may be referred to as S1 for No. 1, S2 for No. 2 and S3 for No. 3. (2) - Gear select switch is the same as the neutral safety switch.
CLEARING DIAGNOSTIC TROUBLE CODES 1) Once all diagnostic trouble codes have been obtained, diagnostic trouble code(s) can be erased from TCM memory by disconnecting electrical connector from TCM for at least 15 seconds. CAUTION: DO NOT disconnect battery, as data stored in other vehicle control modules will be lost. 2) The TCM is located behind right side of instrument panel on Cherokee. See Fig. 1. DRB-II OPERATING MODES NOTE: The DRB-II can be operated in several different modes to perform various tests. Except for voltmeter/ohmmeter and HOW TO USE modes, all other operating modes are selected from AW4 MENU. See ENTERING AW4 MENU under RETRIEVING DIAGNOSTIC TROUBLE CODES. VOLTMETER/OHMMETER MODE To access voltmeter/ohmmeter mode, connect Red volt-ohmmeter test lead to Red port at top right corner of DRB-II. There are 2 different ports on top of DRB-II; ensure test lead is connected to proper port. Access voltmeter or ohmmeter mode using manufacturer's instructions. NOTE: The DRB-II is grounded through transmission diagnostic connector and only one test lead is required. When diagnosing transmission, an external volt-ohmmeter may sometimes be required. HOW TO USE MODE 1) This mode gives instructions on DRB-II usage. To enter this mode, see steps 1) through 4) of ENTERING AW4 MENU under RETRIEVING DIAGNOSTIC TROUBLE CODES. Select 2) HOW TO USE. 2) A series of screens will be displayed explaining DRB-II key usage for system diagnosing. SYSTEM TEST MODE NOTE: SYSTEM TEST mode consists of a stationary test and a road test. The SYSTEM TEST mode must be selected from AW4 MENU. See ENTERING AW4 MENU under RETRIEVING DIAGNOSTIC TROUBLE CODES. 1) Stationary test monitors transmission system data, current valve body solenoid failures, switch failures, correct TCM application, calibration and operation. Road test checks all valve body solenoids and speed sensor. 2) Technician will be instructed to place shift lever in each gear position, starting by shifting into 1-2 position. Once transmission is in Park, brake pedal must be depressed to check brake switch. 3) After brake switch is checked, technician will be instructed to slowly depress throttle. DRB-II will display 7 asterisks (*******) corresponding to throttle position. While depressing accelerator, Throttle Position Sensor (TPS) sweeps through entire range of positions required by the TCM. 4) A corresponding asterisk will be cleared from DRB-II display as each throttle position is sensed by TCM. Several attempts may be required to clear all asterisks from the display, depending on how fast accelerator is depressed. 5) After throttle position is checked, technician will be instructed to drive the vehicle. The DRB-II will indicate if a requested action is seen by the TCM. If technician is requested to perform a particular operation and TCM does not acknowledge the action, press ENTER key to continue testing. 6) The TCM will instruct technician to accelerate vehicle at light throttle to ensure transmission shifts through all gears, indicating proper valve body solenoid operation. 7) During road test, ensure vehicle can be accelerated slowly and evenly to allow transmission to enter all gear ranges without downshifting or braking. If a failure is sensed, a diagnostic trouble code will be displayed on DRB-II. NOTE: If TCM senses a failure, control logic activates a specified valve body solenoid to obtain a certain gear depending on failure. Because transmission diagnostic trouble codes are displayed one at a time, multiple diagnostic trouble codes must be identified by retesting transmission. STATE DISPLAY MODE NOTE: STATE DISPLAY mode must be selected from AW4 MENU. See ENTERING AW4 MENU under RETRIEVING DIAGNOSTIC TROUBLE CODES. Select 3) STATE DISPLAY on DRB-II. Module Information When selecting module information option, the TCM version will be indicated by a 2-digit number. Information can be used to verify proper TCM application. Sensor 1) When selecting sensor option, TPS and RPM indications will be shown. The TPS indicator will display a 7 segment bar graph, indicating TPS position and throttle plate angle. 2) A properly operating TPS should indicate 7 segments through full throttle travel. The RPM indicator will display transmission output shaft revolutions per minute. Brake Switch Or Input/Output Display indicates brake switch status, indicating whether brake pedal is applied or released. Display also indicates shift lever position, whether a valve body solenoid is on or off and present transmission operating gear. DRB-II PROBLEMS & ERROR MESSAGES CARTRIDGE ERROR 1) If CARTRIDGE ERROR message is displayed, disconnect DRB-II from transmission diagnostic connector. DO NOT touch keys on DRB-II keypad. Reconnect DRB-II to transmission diagnostic connector and note display. 2) If CARTRIDGE ERROR message is displayed, replace DRB-II cartridge and proceed with diagnostics. If KEYPAD TEST FAILURE message is displayed, replace DRB-II and proceed with diagnostics. HIGH BATTERY If HIGH BATTERY message is displayed, use external voltmeter to check battery voltage at battery terminals. If battery voltage is 11.7-13.0 volts, replace DRB-II. If battery voltage is not 11.7-13.0 volts, check charging system. KEYPAD TEST FAILURE 1) If KEYPAD TEST FAILURE message is displayed, disconnect DRB-II from transmission diagnostic connector. DO NOT touch keys on DRB-II keypad. Reconnect DRB-II to transmission diagnostic connector and note display. 2) If KEYPAD TEST FAILURE message is not displayed, proceed with diagnostics. If KEYPAD TEST FAILURE message is displayed, replace DRB-II and proceed with diagnostics. LOW BATTERY If LOW BATTERY message is displayed, use external voltmeter to check battery voltage at battery terminals. If battery voltage is 11.7-13.0 volts, replace DRB-II. If battery voltage is not 11.7-13.0 volts, check charging system. RAM TEST FAILURE 1) If RAM TEST FAILURE message is displayed, disconnect DRB- II from transmission diagnostic connector. DO NOT touch keys on DRB-II keypad. Reconnect DRB-II to transmission diagnostic connector and note display. 2) If RAM TEST FAILURE message is not displayed, proceed with diagnostics. If RAM TEST FAILURE message is displayed, replace DRB-II and proceed with diagnostics. If KEYPAD TEST FAILURE message is displayed, replace DRB-II and proceed with diagnostics. COMPONENT TESTING BRAKE SWITCH Brake switch is mounted above brake pedal. When brake pedal is operated, brake switch delivers an input signal to TCM. The TCM uses input signal for controlling No. 3 valve body solenoid for torque converter lock-up. No other information is available from manufacturer. NOTE: For proper brake switch adjustment, see BRAKE SWITCH under REMOVAL & INSTALLATION. NEUTRAL SAFETY SWITCH NOTE: Neutral safety switch may be referred to as park/neutral or gear select switch. For proper neutral safety switch adjustment, see NEUTRAL SAFETY SWITCH under REMOVAL & INSTALLATION. Disconnect electrical connector. Note terminal identification. See Fig. 4. Using ohmmeter, check continuity between specified terminals in relation to shift lever position. See NEUTRAL SAFETY SWITCH CONTINUITY SPECIFICATIONS table. Replace neutral safety switch if continuity is not as specified. NEUTRAL SAFETY SWITCH CONTINUITY SPECIFICATIONS
Shift Lever Continuity Position Between Terminals Park ........................................... "B" & "C" Reverse ........................................ "A" & "E" Neutral ........................................ "B" & "C" Drive ................................................ (1) 3 .............................................. "A" & "G" 1-2 ............................................ "A" & "H" (1) - No continuity should exist between any terminals.
Fig. 4: Identifying Neutral Safety Switch Terminals Courtesy of Chrysler Corp. SPEED SENSOR 1) Disconnect electrical connector at speed sensor located on adapter housing or extension housing. Connect ohmmeter leads between speed sensor electrical terminals. 2) Rotate transmission output shaft and note ohmmeter reading. Ohmmeter needle should fluctuate to indicate speed sensor operation. Replace speed sensor if no reading is obtained. THROTTLE POSITION SENSOR (TPS) NOTE: Digital voltmeter must be used to check TPS. 1) Note location of TPS electrical connector. See Fig. 5. Turn ignition on. Using digital voltmeter, check output voltage at center terminal with throttle plate closed (idle position) and wide open (full throttle) . 2) With throttle plate closed (idle position), output voltage should be greater than 200 millivolts. With throttle plate wide open (full throttle), output voltage should be less than 4.8 volts. 3) Ensure output voltage gradually increases as throttle plate is moved from closed to wide open throttle. If no voltage exists, check for defective wiring circuits or connections. Replace TPS if defective.Fig. 5: Identifying TPS Electrical Connector Courtesy of Chrysler Corp. VALVE BODY SOLENOID With oil pan removed, disconnect electrical connector from valve body solenoid. Using ohmmeter, check resistance between valve body solenoid electrical terminal and solenoid mounting bracket. Replace valve body solenoid if resistance is not 11-15 ohms. TROUBLE SHOOTING CHARTS & CODE CHARTS NOTE: Following trouble shooting charts and illustrations are courtesy of Chrysler Corp. Always start by performing TEST 1A - VERIFICATION OF THE COMPLAINT. When diagnosing transmission, it may be necessary to verify TCM connector terminals, circuits and function, See Fig. 6. NOTE: When using trouble shooting charts, Transmission Control Module (TCM) may be referred to as Transmission Control Unit (TCU). Diagnostic trouble code may be referred to as fault code. Neutral safety switch may be referred to as park/neutral or gear select switch.
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