TEST 3: Testing The Igniter Control Signal

Testing The Igniter Control Signal. How To Test The Igniter -Step By Step (1992, 1993, 1994, 1995 2.2L Toyota Camry)

The igniter control signal (IGT = igniter trigger signal), is the signal that tells it to start activating the ignition coil. Without it, your car is not gonna' start due to a lack of spark.

The IGT signal comes from your Toyota Camry's fuel injection computer (PCM).

The PCM will only send this signal to the igniter after it receives the 2 camshaft signals from the distributor.

IMPORTANT: You'll need to use an automotive LED light with a built in resistor. A 12 Volt test light will not work and can damage the igniter. You can see an example of this LED (with built in resistor) here: The LED Light Test Tool and How To Make One (at: easyautodiagnostics.com).

IMPORTANT: The Igniter must remain connected to its electrical connector for this test to function. To access the IGT signals inside the wire, you'll need to use either a back probe or a wiring piercing probe. You can see an example of a wiring piercing probe here: Wire Piercing Probe Review (Power Probe PWPPPPP01) (at: easyautodiagnostics.com).

These are the test steps:

  1. 1

    Connect the red LED wire to the WHT wire of the igniter's electrical connector. This is the wire that connects to terminal number 2 in the image above (of the igniter's harness connector).

    NOTE: The igniter must remain connected to its electrical connector.

  2. 2

    Connect the black LED wire to the battery negative (-) terminal.

  3. 3

    After the LED light is set up, have your helper crank the engine as you observe the LED light.

  4. 4

    The LED light should flash ON and OFF in steady pulses as the engine is cranking if the IGT signal is present.

Let's take a look at what your test results mean:

CASE 1: The LED light flashed as the engine was cranked. This is the correct and expected test result and tells you that the igniter is getting the IGT control signal from the fuel injection computer.

You can now conclude that the igniter is bad if you have:

  1. Made sure the ignition coil is not sparking and not getting the IGC signal from the igniter.
  2. Made sure the igniter has power (TEST 1).
  3. Made sure the igniter has Ground (TEST 2).
  4. Made sure the igniter is getting the IGT signal from the fuel injection computer (TEST 3).

CASE 2: The LED light DID NOT flash when you cranked the engine. This tells you that the igniter is not activating the ignition coils due to a lack of the IGT control signal.

The most common reason the IGT signal is missing is a defective camshaft position sensor. Your next step is to go to: TEST 4: Testing Camshaft Position Sensor 1.

TEST 4: Testing Camshaft Position Sensor 1

In this test section we're gonna' test camshaft position (CMP) sensor 1 inside the distributor by measuring the A/C voltage it produces, as we crank the engine, with a multimeter.

If you have an oscilloscope, then in photo 2 of 2 (in the image viewer above), you'll find the waveforms for both CMP sensors. The oscilloscope settings that I used were: Time/DIV 100ms, Volt/DIV: 2 Volts, Attenuation: 1X.

IMPORTANT: This test is done on the distributor's 4 pin connector. You'll need to use test lead with insulated crocodile tips to attach your multimeter to the male spade terminals indicated in the test steps below.

These are the test steps:

  1. 1

    Disconnect distributor 4 pin connector from its 4 wire connector.

    This is the connector that connects to the camshaft position sensors within the distributor.

  2. 2

    Connect one multimeter test lead to terminal #1 of the distributor connector.

  3. 3

    Connect one multimeter test lead to terminal #2 of the distributor connector.

  4. 4

    Place your multimeter in Volts AC mode.

  5. 5

    Have your helper crank the engine once you have set up the multimeter test leads.

  6. 6

    Your multimeter should register a reading that should oscillate between 0 and 0.2 Volts AC as the engine turns if the camshaft position sensor is functioning.

Let's take a look at what your test results mean:

CASE 1: The CMP sensor produced the indicated AC Voltage. This is the correct and expected test result and tells you that CMP sensor 1 is OK.

The next step is to test CMP sensor 2. Go to: TEST 5: Testing Camshaft Position Sensor 2.

CASE 2: The CMP sensor DID NOT produce the indicated AC Voltage. This tells you that the camshaft position sensor is defective.

This lack of CMP 1 signal will keep the PCM from activating the igniter. In turn, the igniter won't activate the ignition coil. Replace the distributor (since the CMP sensors are not sold separately).