Notes on Circuit Inspection
^ Intermittent troublesMost intermittent problems are caused by faulty electrical connections or wiring.
Perform careful check of suspect circuits for:
- Poor mating of connector halves, or terminals not fully seated in connector body (backed out).
- Improperly formed or damaged terminals. All connector terminals in problem circuit should be carefully reformed to increase contact tension.
- Poor terminal to wire connection.
^ Never connect any tester (voltmeter, ohmmeter, or whatever) to ECM when its connector is disconnected. Attempt to do it may cause damage to ECM.
^ Never connect an ohmmeter to ECM with its connector connected to it. Attempt to do it may cause damage to ECM and sensors.
^ Be sure to use a voltmeter with high impedance (Mn/V minimum) or a digital type voltmeter. Any other voltmeter should not be used because accurate measurements are not obtained.
^ When checking voltage at each terminal of the connector which is connected to ECM, be sure to negative probe to body ground. Any other way is prohibited even by accident. Applying it improperly may cause the sensor or ECM to be shorted and damaged.
Checking Voltage And Terminal Position:
^ For ECM connector terminal positions (A1, A2 ... to A24 and B1, B2 ... to B17), refer to illustration.
^ When disconnecting and connecting connector, make sure to turn ignition switch OFF.
^ When there is a question "Are couplers connected properly?" in FLOW CHART, check male half of terminal for bend and female half for excessive opening, terminal for poor locking (looseness), corrosion, dust, etc.
Connecting Meter Probe:
^ When connecting a probe of ohmmeter, voltmeter, etc. to connector terminal, be sure to connect it from wire harness side of connector.
Connecting Meter Probe:
^ When connecting meter probe from terminal side of connector because it can't be connected from harness side, use extra care not to bend male terminal of connector or force its female terminal open for connection.
In case of such connector as shown below, connect probe as shown below to avoid opening female terminal.
^ Never connect probe where male terminal is supposed to fit.
^ Before measuring voltage at each terminal, check to make sure that battery voltage is 11V or higher. Such terminal voltage check at low battery voltage will lead to erroneous diagnosis.