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 coupler halves, or terminals not fully seated in coupler body (backed out).
Improperly formed or damaged terminals. All coupler terminals in problem circuit should be carefully reformed to increase contact tension.
- Poor terminal to wire connection.
^ 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.
^ Never connect any tester (voltmeter, ohmmeter, or whatever) to ECM when its coupler is disconnected. Attempt to do it may cause damage to ECM.
^ Never connect an ohmmeter to ECM with its coupler connected to it. Attempt to do it may cause damage to ECM and sensors.
^ Be sure to use a voltmeter with high impedance (m Ohms/V minimum) or a digital type voltmeter. Any other voltmeter should not be used because accurate measurements are not obtained.
^ When disconnecting and connecting coupler, make sure to turn ignition switch OFF, or ECM may get damaged.
^ When connecting a probe of ohmmeter, voltmeter, etc. to coupler terminal, be sure to connect it from wire harness side of coupler.
^ When connecting meter probe from terminal side of coupler because it can't be connected from harness side, use extra care not to bend male terminal of coupler or force its female terminal open for connection.
In case of such coupler as shown at the left, connect problem as shown 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.
^ When checking voltage at each terminal of the coupler which is connected to ECM, be sure to connect 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.