Mazda Trucks 1994-1998 Repair Guide

Diagnosis and Testing

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SERVICE PRECAUTIONS





Always turn the key OFF and isolate both ends of a circuit whenever testing for shorts or continuity.
 
Never measure voltage or resistance directly at the processor connector.
 
Always disconnect solenoids and switches from the harness before measuring for continuity, resistance or energizing by way of a 12-volt source.
 
When disconnecting connectors, inspect for damaged or pushed-out pins, corrosion, loose wires, etc. Service if required.
 

PRELIMINARY CHECKS



  1. Visually inspect the engine compartment to ensure that all vacuum lines and spark plug wires are properly routed and securely connected.
  2.  
  3. Examine all wiring harness and connectors for insulation damage, burned, overheated, loose or broken conditions. Ensure that the ICM is securely fastened to the front fender apron.
  4.  
  5. Be certain that the battery is fully charged and that all accessories are OFF during the diagnosis.
  6.  

TEST PROCEDURES



Perform the test procedures in the order in which they are presented here.

Ignition Coil Secondary Voltage Test
CRANK MODE
  1. Connect a spark tester between the ignition coil wire and a good engine ground.
  2.  
  3. Crank the engine and check for spark at the tester.
  4.  
  5. Turn the ignition switch OFF.
  6.  
  7. If no spark occurs, check the following:
    1. Inspect the ignition coil for damage or carbon tracking.
    2.  
    3. Check that the distributor shaft is rotating when the engine is being cranked.
    4.  

  8.  
  9. If a spark did occur, check the distributor cap and rotor for damage or carbon tracking. Go to the Ignition Coil Secondary Voltage (Run Mode) Test.
  10.  

RUN MODE
  1. Fully apply the parking brake. Place the gear shift lever in Neutral (manual transmission) or Park (automatic transmission).
  2.  
  3. Disconnect the S terminal wire at the starter relay. Attach a remote starter switch.
  4.  
  5. Turn the ignition switch to the RUN position.
  6.  
  7. Using the remote starter switch, crank the engine and check for spark.
  8.  
  9. Turn the ignition switch OFF .
  10.  
  11. If no spark occurred, the problem lies with the wiring harness. Inspect the wiring harness for short circuits, open circuits and other defects.
  12.  
  13. If a spark did occur, the problem is not in the ignition system.
  14.  

Spark Timing Advance Test (1994 B Series Pick-up with 3.0L engine)

Spark timing advance is controlled by the engine control module. This procedure checks the capability of the ignition module to receive the spark timing command from the engine control module. The use of a volt/ohmmeter is required.

  1. Turn the ignition switch OFF.
  2.  
  3. Disconnect the pin-in-line connector (SPOUT connector) near the TFI module.
  4.  
  5. Start the engine and measure the voltage, at idle, from the SPOUT connector to the distributor base. The reading should equal battery voltage.
  6.  
  7. If the result is okay, the problem lies within the EEC-IV system.
  8.  
  9. If the result was not satisfactory, separate the wiring harness connector from the ignition module. Check for damage, corrosion or dirt. Service as necessary.
  10.  
  11. Measure the resistance between terminal No. 5 and the pin-in-line connector. This test is done at the ignition module connector only. The reading should be less than 5 ohms.
  12.  
  13. If the reading is okay, replace the TFI module.
  14.  
  15. If the result was not satisfactory, service the wiring between the pin inline connector and the TFI connector.
  16.  

 
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