Intermittent conditions of automatic transmission (AWR6B45)

1. Intermittent conditions of automatic transmission description of symptom

1. Required preliminary inspection

Before performing the Intermittent conditions of automatic transmission, perform the Diagnostic system check-transmission controls to verify that all the following conditions are met.

  • The transmission control system operates normally.
  • The check trans warning light is operating normally.
  • No DTCs are set.
  • The scan tool data is within the range of normal values.

2. Visual inspection

Some of the procedures require a careful visual and physical inspection. Problems may be solved just by carrying out visual and physical inspections, which leads to saving valuable time. Check for the following conditions.

  • There is no contamination or improper tightening in the ground terminal.
  • The ground terminal is installed in the correct position.
  • The wire harness and terminals are properly connected.
  • The wire harness is not pinched or cut.

3. Intermittent conditions

Intermittent conditions indicate the following.

  • The problem is not currently present but is recorded in the DTC history.
  • There is a customer complaint, but the symptom cannot currently be reproduced because the problem is not DTC-related.

If an intermittent condition exists, inspect for improperly installed electrical components. Inspect the installation status of any aftermarket electronic equipment, lights, etc. Verify that no aftermarket electronic equipment is connected to the serial data circuit. When a problem occurs, the check trans warning light may not illuminate or a DTC may not be stored. Most intermittent conditions are caused by a defective wire harness or poor connections. Carefully inspect suspected connectors visually and physically for the following conditions.

  • Poor connections at the connector
  • Terminal looseness
  • Damaged or improperly formed terminals

Repair or replace connector terminals in the problem circuit in order to ensure proper contact pressure. It is necessary to remove the terminal from the connector body in order to inspect for poor terminal-to-wire harness connections. Connect the DMM to the suspected circuit and perform a vehicle road test. Changes in the readings that follow any malfunctions that occur are good indications that there is a malfunction in the circuit being monitored. If an intermittent condition exists from the start and continues, inspect for improperly installed electrical components such as lights.
If any of the following is the cause of the problem, no DTC is stored, but the check trans warning light illuminates intermittently.

  • There is contamination or improper tightening in the ground terminal.
  • There is an intermittent short to the check trans warning light ground circuit.
  • An electrical surge is generated by a relay, solenoid, or switch malfunction.
  • There are open diodes.

Note

  • A relay, solenoid, or switch malfunction may cause the generation of a large surge voltage or surge current. Normally, this problem will occur when the malfunctioning component is operating.

The following inspection items show possible causes for each symptom. There is no order to these procedures. If there are no abnormal scan tool readings, proceed in a logical order, starting with items that are easiest to inspect, or those that are most likely.

1) Wire harness and connector

Intermittent open or short circuits in the circuit may be affected by the movement of wire harnesses and connectors due to vibrations, fluctuations in engine torque, bumps in the road, rough pavement, etc. Perform the following inspections if possible.

  • Move the related connectors or wiring while monitoring the applicable scan tool data.
  • Move the related connectors or wiring and monitor component operation while commanding the components ON and OFF using the scan tool.
  • With the engine running, move related connectors or wiring while monitoring engine operation.

If moving the wire harness or connector affects the data displayed, the component/system operation, or engine operation, inspect the wire harness or connector, and repair as necessary.

2) Electrical connections or wiring

Intermittent conditions are caused by poor wire harness connections, loose terminals, or problems in the wire harness. Check for the following conditions.

  • Is the connector connected to the improper part?
  • Are there any abnormal conditions in the terminals installed in the connector body?
  • Are there any improperly formed or damaged terminals?
  • Is there looseness in the terminals?
  • Are there any poor terminal-to-wire harness connections or bent terminals?
  • Is there any corrosion or water intrusion?
  • Are there any broken wire harnesses?
  • Is the wire harness pinched, cut, or damaged?
  • Is the wire harness coming in contact with hot exhaust components?

Note

  • Worn or damaged insulation can allow moisture to enter the wiring. The conductor can corrode inside the insulation, with little visible evidence. Check for swollen or stiff sections of the wire harness in the suspected circuits.

3) Control unit power supply and ground, component power supply and ground

Poor power supply or ground connections can cause widely varying symptoms.
The control unit may have multiple power supply circuits, and there are also some system components that are connected to power supply circuits from locations other than the control unit. Inspect all control unit power supply circuits. It is also necessary to inspect the intermediate connections. A test lamp or a DMM is capable of indicating whether or not any voltage is present, but neither of them has the ability to determine whether sufficient current is flowing in the circuit. Check that the circuit can carry the current necessary to operate the components.
The control unit may have multiple ground circuits, and there are also some system components that are connected to ground circuits from locations other than the control unit. Inspect all control unit and system ground circuits. Inspect the ground terminals for improper tightening or dirt. Also inspect the connections at the component and in splice packs where applicable. Check that the circuit can carry the current necessary to operate the components.

4) Effects caused by temperature

An intermittent condition may occur when a component reaches the appropriate operating temperature. It may also occur only when the temperature is high or low.
If the intermittent condition is caused by heat, check the data relating to the following items.

  • High ambient temperature
  • Heat emitted from the underhood or engine
  • Heat generated due to poor wire harness connections or a high electrical load
  • Heat generated due to high load conditions such as towing.

If the intermittent condition is attributed to low temperature, check the data related to the following items.

  • Low ambient temperature
  • The symptom occurs only on a cold start.
  • The symptom goes away when the vehicle warms up.

Note

  • If the temperature is extremely low, a connection area or component may freeze. Inspect for water intrusion.

Based on the information from the customer, determine if the malfunction is caused by temperature.

5) Electromagnetic interference (EMI) and electrical noise

Some electronic components and circuits are sensitive to EMI or other types of electrical noise.
Inspect for wire harnesses that are placed too close to high-voltage or high-current components such as injection components, motors, and generators. These components may generate electrical noise which interferes with normal circuit operations.
Check for a surge voltage or surge current generated by a relay, solenoid, or switch malfunction. Normally, this problem will occur when the malfunctioning component is operating.
Inspect for improper installation of non-factory or aftermarket electronic equipment such as lights, radios, amplifiers, electric motors, remote starters, and alarm systems. Electromagnetic disturbance may occur while the electronic equipment is in use, but not when not in use.
Inspect for an open diode. There may be a bent diode in the relay.
Inspect the generator for a malfunctioning rectifier circuit that may be allowing AC noise into the electrical system.

4. Duplicating failure conditions

Operate the vehicle with the DMM connected to the suspected circuit. An abnormal reading on the DMM when the problem occurs may help identify the problem.

5. Scan tool snapshot

The scan tool snapshot function allows the recording of data collected by the control unit. The snapshot function records data in chronological order and can perform data analysis from the recorded data. The scan tool also has a graph function which can be used to graph parameters individually or in combination with other parameters for comparison. The snapshot can be triggered manually at the time the symptom is noticed or set up in advance to be triggered when a DTC sets. Using the abnormal values in the recorded data, it is possible to identify systems and components that require detailed investigation.