Learning Guide CHASSIS ELECTRICAL SPECIALIST AUTOMATIC TRANSMISSION IN-CAR DIAGNOSTICS COURSE NUMBER: C050-01
Notice Due to the wide range of vehicles makes and models, the information given during the class will be general in nature and should not be taken as specific to any vehicle/unit. Please consult manufacturer specifications for the correct number/specifications and repair procedures for the vehicle you are testing. This document is meant to be used as a guideline only. For further information, please contact toll-free: 1-855-813-2101 or email info@carstraining.net No part of this book may be reproduced, stored in any retrieval system or transmitted in any form or by any means (including but not limited to electronic, mechanical, photocopying and recording) without prior written permission of CARS Training Network Inc. This applies to all text, illustrations, tables and charts. Copyright 2014 CARS Training Network Inc Page ii
Objectives Upon successful completion of this segment the participant will be able to: Identify different fluid types Review input sensors output functions for Caravan and Voyager electronic transmission Describe CVI (Clutch Volume Index) Describe theory and operation of Taurus/Sable electronic transmission Perform In-Car Diagnostic testing of both units Rationale Many automatic transmission problems can be fixed quickly and accurately without subletting the vehicle to a transmission specialty shop. Knowing how to diagnose and repair common transmission problems will increase the number of jobs technicians perform successfully. Note Due to the wide range of vehicles makes and models, the information given during the class will be general in nature and should not be taken as specific to any vehicle/unit. Please consult manufacturer specifications for the correct number/specifications and repair procedures for the vehicle you are testing. This document is meant to be used as a guideline only. Page 1
Types of Automatic Transmission Fluid (ATF) Chrysler, Ford, General Motors and some import vehicle manufacturers all have their own ATF specifications. Automatic transmission fluids possess different frictional properties, producing different shift characteristics. ATF must be matched to friction materials and vehicle design. When choosing a transmission fluid: The fluid must meet or exceed OEM specifications The fluid must be the correct type to be used in the specific application The recommended fluid type is listed on many dipsticks. If not, check the owner s manual or appropriate service material. Chrysler Fluid: Started with Dexron Updated to ATF+2 1998: Updated to ATF+3, increased shear stability and high temperature resistance to oxidation 2000: Introduced ATF+4, recommended for all Chrysler transmissions excluding 1999 and earlier minivans General Motors Fluid: Dexron-III replaces Dexron and Dexron-II, friction-modified and improved oxidation resistance GM T-4 used for Pontiac Vibe and Toyota Matrix, same as Chrysler ATF+4 Ford Fluid: Type F used on early transmissions Mercon used on 1988 and later transmissions, not recommended for Type F or the new Mercon V Mercon V introduced in 1997 on certain transmissions Honda Fluid: Honda ATF-Z1 Most other imports: Usually requires Dexron-III, Always check OEM requirements Page 2
Dodge Caravan and Plymouth Voyager 41TE Automatic Transmission Introduced in 1989, several updates, still used in 2005. Transmission Control Module The TCM is the control unit for all transaxle electronic operations. The TCM receives information regarding vehicle operation from both direct and indirect inputs, and selects the operational mode of the transaxle. Direct inputs are hardwired to (and used specifically by) the TCM. Indirect inputs originate from other components or modules, and are shared with the TCM via the communication bus. TCM Inputs: Direct Inputs Indirect Inputs Battery (B+) voltage Engine/Body Identification Ignition ON voltage Manifold Pressure Transmission Control Relay (Switched B+) Target Idle Throttle Position Sensor Torque Reduction Confirmation Crankshaft Position Sensor (CKP) Speed Control ON/OFF Switch Transmission Range Sensor (TRS) Engine Coolant Temperature Transmission Temperature Sensor (Integral to TRS) Ambient/Battery Temperature Pressure Switches (L/R, 2/4, OD) Brake Switch Status Input Shaft Speed Sensor DRB Communication Output Shaft Speed Sensor Page 3
The TCM determines the appropriate shift schedule and shift points based on information received from these inputs, considering operating conditions and driver demand. Examples of TCM direct outputs: Transmission Control Relay Solenoids (LR/CC, 2/4, OD and UD) Vehicle Speed (to PCM) Torque Reduction Request (to PCM) In addition to monitoring inputs and controlling outputs, the TCM also: Stores and maintains Clutch Volume Indices (CVI) Stores and selects appropriate Shift Schedules System self-diagnostics Diagnostic capabilities (with DRB scan tool) Limp-Home Mode When TCM is unable to control transmission (or senses operational problems) it defaults to Limp-home mode. The shift solenoids are normally open, which by design allows fluid flow in their relaxed or OFF state, even with no electrical power at all transmission has 2 nd forward and manually shifted reverse. Page 4
Solenoid/Pressure Switch Assembles Externally mounted to case, serviced as a complete unit Solenoids receive power from Transmission Control Relay Ground provided by TCM Updated in 1999 to reduce operating noise Updated gasket for better sealing New design solenoid pack will retro-fit all 41TE transmissions Contain three pressure switches that monitor hydraulic circuits Primary function (of pressure switches) is detecting clutch circuit hydraulic failure DTC sets if TCM senses any switch open or closed at the wrong time in a given gear Solenoid continuity is periodically tested: each solenoid is turned on or off depending on its current state. TCM should detect an inductive spike, if voltage spike is not detected circuit is tested again to verify failure, resulting in a DTC. Page 5
Clutch Volume Index An important function of TCM is to determine Clutch Volume Index (CVI). CVI represents the volume of fluid needed to compress a clutch pack. The TCM monitors gear changes by monitoring Input and Output speed sensors. For example, if input rpm is 1000 and output is 500 TCM determines gear ratio of 2:1, in 3rd gear ratio is 1:1, by monitoring the length of time it takes for a gear ratio change following a shift request, TCM can determine the volume of fluid needed to apply that particular clutch pack. The volume of fluid needed is constantly updated for adaptive controls. As friction material wears, the volume of fluid needed increases. CVI is a direct indication of transmission state, the higher CVI the higher the wear on the clutch packs. CLUTCH VOLUMES When Updated Proper Clutch Volume Clutch Shift Sequence Oil Temperature Throttle Angle CVI L/R 2-1 or 3-1 coast downshift > 70 < 5 35 to 83 2/4 1-2 shift 20 to 77 5-54 OD 2-3 shift > 110 48 to 150 UD 4-3 or 4-2 shift > 5 24 to 70 NOTES: Page 6
Input Speed Sensor Located towards front of transmission Provides information on how fast input shaft is spinning Will be lower than engine rpm due to slippage in torque converter Two wire magnetic pick-up (generates AC signal) TCM (Transmission Control Module) uses sensor for input shaft RPM Used to monitor TCC slippage Output Speed Sensor In 1998 Vehicle speed sensor was eliminated, PCM uses output speed sensor to calculate vehicle speed Provides information on how fast output shaft is spinning TCM compares input and output, to determine gear position TCM monitors how long it takes to change gears to Calculate CVI Page 7
Transmission Range Sensor In 1996 the PRNODL and Neutral Safety Switch were replaced with TRS Used for Vehicle Start-up, Reverse lights, Forward, Reverse and Converter Clutch strategies Mounted to the top of valve body--can only be serviced by removing valve body TRS has an integrated temperature sensor (thermistor) to monitor transmission sump temperatures PCM/TCM uses this information to determine shift points and to energize cooling fan s when a transmission overheat condition exists Throttle Position Sensor Potentiometer, PCM sends 5 volt reference and determines throttle angle from return voltage TCM uses this information to determine shift points and for TCC operation Also used for kick-down operation Page 8
Transaxle Quick Learn Procedure The quick learn procedure requires a scan tool. This program allows system to recalibrate itself. Since the TCM keeps CVI (Clutch Volume Index) in memory, when changes are made to transaxle system the TCM will apply amounts of fluid that apply to old clutch pack values. The Quick Learn Procedure should be performed after: Transaxle Assembly Replacement Transmission Control Module Replacement Solenoid/Pressure Switch Assembly Replacement Clutch and/or Seal Replacement Valve Body Replacement Pinion Factor Procedure The vehicle speed readings for the speedometer are taken from the output speed sensor (the vehicle speed sensor was eliminated in 1998). The TCM must be calibrated to the different combinations of equipment available. Pinion Factor allows the technician to set the TCM initial settings so that the speedometer will be accurate. Torque Reduction Management Torque management controls torque of the engine during certain shift sequences, reducing torque applied to clutch packs. The torque management signal is a 12 volt signal, sent from PCM to TCM over the Torque Reduction Link (TRL). Torque management is requested when TCM grounds this signal. PCM recognizes the request, retards ignition timing and kills injectors. Torque reduction is not noticeable to the driver and usually lasts a short period of time. PCM sends a confirmation of request to the TCM via the communication line. If confirmation isn t received by the TCM after two requests, a DTC sets. Page 9
Taurus/Sable Electronic Transmission In 1997 and later models the Manual Lever Position sensor (Neutral safety switch) was replaced with a Digital Range Sensor (DRS). They are not interchangeable Vehicle build date determines which sensor is used MLP will plug into a DRS but transmission will not function properly. DRS receives 5 volt reference Sets of resistors allow different return voltages to the PCM PCM uses return voltage to determine Range selection Input Speed Sensor Magnetic pick-up, sends turbine shaft speed to PCM PCM monitors TCC application by comparing engine rpm to ISS. O-ring Electrical Connector Speed Sensor Used in determining EPC (Electronic Pressure Control) at idle Sensor malfunction may cause harsh shifts, lack of 4th gear and no TCC Serviceable, located by drivers side half shaft Magnetic Pickup Output Carrier Rotor or Forward Clutch Gear Teeth Output Speed Sensor VSS (Vehicle Speed Sensor) was eliminated (starting with some 1999 models) Magnetic pick-up, sends output shaft speed to PCM PCM compares input to output to determine gear ratio PCM uses information to determine actual vehicle speed Is serviceable and is located on top of case by pass side half shaft Page 10
TCC Torque Converter Clutch Solenoid Serviceable, mounted on inside of side cover PWD (Pulse Width Modulated) for smooth applications PCM applies Converter Clutch in steps that can be observed with scan tool Monitors slippage by comparing engine RPM to input Speed sensor --referred to as TCCMACT on scan tool If solenoid fails in ON position, engine will run rough and stall at low vehicle speeds If solenoid fails in OFF position, TCC will not operate EPC Electronic Pressure Control Solenoid Variable-Force Style Solenoid (VFS) Receives commands from PCM and adjusts hydraulic pressure 12 volt system Electro-hydraulic actuator combines a solenoid and regulating valve PCM has an adaptive learn strategy, automatically adjusting line pressure for shift feel Fail Safe EPC fails to maximum line pressure resulting in harsh engagements and shifts If battery power disconnected, it should remain disconnected for 20 minutes to reset adaptive shift pressure strategy--or use scan tool and perform Keep Alive Memory reset 12 volts PWM: the higher the voltage the higher line pressure Page 11
Throttle Position Sensor Direct relationship between TPS and EPC: as throttle angle increases, line pressure increases TPS fail safe will cause full (EPC) line pressure to protect transaxle TPS value remaining stationary at idle will result in low line pressure, may result in transaxle damage TPS value remaining stationary at WOT results in very harsh shifts TPS will affect TCC operation Shift Solenoids Key-On ignition power Ground provided by PCM 3 solenoids used individually or in different combinations Mounted on valve body behind side cover Chart below shows solenoid application during each gear Gear Position SS1 SS2 SS3 Park Off On Off Reverse Off On Off Neutral Off On Off Overdrive OD1 Off On Off OD2 Off Off Off OD3 On Off On OD4 On On On Page 12
Engine Coolant Temperature Sensor PCM uses sensor information in controlling TCC Defective ECT results in no TCC Extremely low or high temperatures affect TCC operation Transmission Temperature Sensor Located inside main valve body Resistance of thermistor changes with fluid temperature change PCM inhibits TCC operation and adjusts EPC pressure for cold temperatures Brake Switch Defective, inoperative or misadjusted brake pedal switch will prevent TCC engagement Transmission Coolers Some vehicles have thermostats inside transmission coolers Attempting to flush these coolers after a transmission failure may not be possible or recommended 1 - MOUNTING BOLTS 2 - THERMOSTATIC BYPASS VALVE 3 - RADIATOR 4 - QUICK-CONNECT FITTINGS 5 - TRANSMISSION OIL COOLER 1 - THERMOSTAT HOUSING 2 - SPRING 3 - END PLUG 4 - SNAP RING 5 - THERMOSTAT Page 13