TEST 3: Testing The Igniter Control Signals
All right, if you've reached this point, you have:
- Confirmed that two or all four cylinders have no spark.
- Confirmed that the igniter is getting power (TEST 1).
- Confirmed that the igniter is getting Ground (TEST 2).
In this test section we're now gonna see if the fuel injection computer is activating the igniter.
The fuel injection computer, after receiving a crankshaft position sensor signal, starts to send two activation signals to the igniter.
These two igniter activation signals are referred to as IGT1 and IGT2. These signals are what tell the igniter to start activating the ignition coils.
In this test section we'll check for the presence of these two signals, while cranking the engine, with an LED light.
IMPORTANT: Do not use a 12 Volt test light instead of an LED light, or you'll damage the igniter. If you need to buy an LED light, go 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 on the connector 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
Connect the red LED wire to the GRY wire of the igniter's electrical connector.
The GRY wire connects to female terminal number 5 in the illustration of the connector above.
NOTE: The igniter must remain connected to its electrical connector. - 2
Connect the black LED wire to the battery negative (-) terminal.
- 3
After the LED light is set up, have your helper crank the engine as you observe the LED light.
- 4
The LED light should flash ON and OFF in steady pulses as the engine is cranking if the IGT1 signal is present.
- 5
Repeat steps 1 thru 4 on the BLU/YEL wire to test for the IGT2 signal.
The BLU/YEL wire connects to female terminal number 4 in the illustration of the connector above.
Let's take a look at what your test results mean:
CASE 1: The LED light flashed on both circuits (wires) tested. This is the correct and expected test result and tells you that the igniter is getting the IGT1 and IGT2 control signals from the fuel injection computer.
The next step is to make sure that the igniter is now creating the activation signal for the 1/4 ignition coil and the 2/3 ignition coil. For this step, go to: TEST 4: Testing The Ignition Coil Control Signals.
CASE 2: The LED light DID NOT flash on both circuits (wires) tested. This tells you that the igniter is not activating the ignition coils due to a lack of the IGT control signals.
The most common reason the IGT1 and IGT2 signals are missing is a defective crankshaft position sensor. The following tutorial will help you test the CKP sensor:
CASE 3: The LED light flashed on one but NOT BOTH circuits (wires) tested. Recheck your connections and repeat the test.
If the LED light still does not confirm the presence of both IGT signals, then the most likely causes of this missing IGT signal is:
- An open-circuit problem in the wiring between the igniter's connector and the fuel injection computer's connector.
- A bad fuel injection computer.
TEST 4: Testing The Ignition Coil Control Signals
All right, for our last test, we're now gonna see if the igniter is creating and delivering activation signals to the ignition coils.
These two signals are known as the IGC1 and IGC2 signals.
The ignition coil activation signals can be tested in quite a few different ways. In this tutorial we're going to use and LED light to check for their presence.
IMPORTANT: The igniter must remain connected to its electrical connector for this test to function.
These are the test steps:
- 1
Disconnect the 1/4 ignition coil from its electrical connector.
- 2
Connect the red LED wire to the female terminal labeled with the number 1 of the ignition coil harness connector (see illustration above).
The wire that connects to terminal 1 is a black with white stripe (BLK/WHT) wire.
CAUTION: You'll connect the LED wire to the female terminal of the connector. Do not insert a large diameter test lead into the female terminal of the ignition coil connector, or you'll damage the female terminal! - 3
Connect the black LED wire to the terminal labeled with the number 2 of the ignition coil harness connector (see illustration above).
The wire connecting to terminal 2 is a red (RED) wire. - 4
After the LED light is set up, have your helper crank the engine as you observe the LED light.
- 5
The LED light should flash ON and OFF as the engine cranks.
- 6
Repeat steps 1 thru 5 on the 2/3 ignition coil harness connector to test for the IGC2 signal.
NOTE: On 2/3 ignition coil connector, terminal 2 has a red with white stripe (RED/WHT) wire and terminal 1 is a BLK/WHT.
Let's interpret your test result:
CASE 1: The LED light flashed on both ignition coil connectors. This is the correct and expected test result and tells you that the igniter is creating and sending the IGC1 and IGC2 control signals to the ignition coils.
This test result also confirms the igniter (ignition control module) is functioning correctly.
You can conclude that both ignition coils are bad and need replacement only if you have confirmed that:
- All four cylinders are not getting spark.
- The igniter is getting battery power and Ground (TEST 1 and 2).
- The igniter is getting both the IGT1 and IGT2 signals (TEST 3).
- The igniter is creating/sending the IGC1 and IGC2 signals to the ignition coils (this test section).
CASE 2: The LED light DID NOT flash on both ignition coil connectors. This tells you that the igniter is bad.
You can conclude that the igniter is defective and needs replacement only if you have tested and confirmed that:
- All four cylinders are not getting spark.
- The igniter is getting battery power and Ground (TEST 1 and 2).
- The igniter is getting both the IGT1 and IGT2 signals (TEST 3).
- The igniter IS NOT creating/sending the IGC1 and IGC2 signals to the ignition coils (this test section).
CASE 3: The LED light flashed ON and OFF on one but NOT BOTH ignition coil connectors. This tells you that the igniter is bad.
You can conclude that the igniter is defective and needs replacement only if you have tested and confirmed that:
- One ignition coil is sparking, but the other is not.
- The igniter is getting battery power and Ground (TEST 1 and 2).
- The igniter is getting both the IGT1 and IGT2 signals (TEST 3).
- The igniter is only sending one IGC signal to one but not the both ignition coils (this test section).
More 1.5L Toyota Tercel Tutorials
You can find a complete list of 1.5L Toyota Tercel tutorials and wiring diagrams in this index:
Here's a sample of the tutorials you'll find in the index:
- How To Test The Igniter -Step By Step (1995-1996 1.5L Toyota Tercel).
- How To Test Engine Compression (1.5L Toyota Tercel).
- How To Test The Fuel Injectors (1995-1996 1.5L Toyota Tercel).
- How To Test For A Blown Head Gasket (1.5L Toyota Tercel).
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