This tutorial will help you test the Ignitor (ignition control module) on the 1995 thru' 1996 1.5L Toyota Tercel. You don't need any expensive diagnostic tools to follow the test instructions, since I'll be showing you how to test it using a simple LED light.
I've also included the Oscilloscope wave form patterns for the IGT control signals you'll need to see if you're using one.
Contents of this tutorial at a quick glance:
- Symptoms of Bad Ignitor.
- Ignitor Circuit Descriptions.
- Basic Operation Theory Of The Ignitor.
- TEST 1: Testing For Spark At All 4 Cylinders.
- TEST 2: Making Sure The Ignitor Is Getting Power.
- TEST 3: Making Sure The Ignitor Is Getting Ground.
- TEST 4: Testing The Ignitor Control Signals.
- TEST 5: TEST 5: Testing The Ignition Coil Control Signals.
- Where To Buy The Ignitor (Ignition Control Module).
NOTE: You can find the Ignitor wiring diagram here: Ignitor Wiring Diagram 1995-1996 1.5L Toyota Tercel.
Symptoms Of A Bad Ignitor
The Ignitor (which is another name for the ignition control module) is the component that activates the ignition coils sitting on top of the engine's valve cover. When this bad boy fails, your Toyota Tercel is not gonna' start due to a lack of spark (at all four cylinders).
What gives away the Ignitor as defective, when testing it, is the fact that it's getting battery power, ground, and it's two Ignitor control signals from the fuel injection computer but it does not activate the ignition coils to fire spark away.
Ignitor Circuit Descriptions
The Ignitor (ignition control module) has 8 wires coming out of its connector. Each one has a specific job to do and here's a brief description of each:
|1995-1996 1.5L Tercel Ignitor Connector|
|1||Red with white stripe||IGC2 -2/3 Ignition coil control signal|
|2||Light green with black stripe||IGF -Ignition coil firing feedback|
|3||White with black stripe||GND -Chassis ground|
|4||Blue with yellow stripe||IGT2 -Ignitor control signal cylinders 2/3|
|5||Light green||IGT1 -Ignitor control signal cylinders 1/4|
|6||Black with blue stripe||TACH -Tachometer signal|
|7||Black with orange stripe||+B -Battery power|
|8||Red||IGC1 -1/4 Ignition coil control signal|
NOTE: The Ignitor harness connector has female metal terminals. You'll need to use a back probe or a wiring piercing probe to test the signals in the wires.
Basic Operation Theory Of The Ignitor
In a nutshell, when you turn the key and crank the engine:
- The Ignitor gets battery power on the Ignitor harness connector terminal #7 (see illustration above).
- The wire that feeds battery power to the Ignitor is the black with orange stripe (BLK/ORG) wire.
- This same circuit also feeds battery power to the ignition coils.
- The crankshaft and camshaft position sensors start to generate their signals. These signals are transmitted directly to the fuel injection computer.
- Once the fuel injection computer gets the crank and cam position signals, it sends two Ignitor (IGT) control signals to the Ignitor. The IGT signals are what tell the Ignitor to start activating the ignition coils.
- The signal to activate the 1/4 ignition coil is received on terminal #5. The color of the wire is light green (LT GRN). This circuit is labeled as IGT1
- The signal to activate the 2/3 ignition coil is received on terminal #4. The color of the wire is blue w/ yellow stripe (BLU/YEL). This circuit is labeled as IGT2
- When the Ignitor receives the Ignitor control signals, it now activates the ignition coils by switching the ignition coils' primary circuits ON and OFF:
- Ignition coil for cylinders 1/4 is activated thru' the red (RED) wire. This circuit is known as the IGC1 circuit.
- Ignition coil for cylinders 2/3 is activated thru' the red with white stripe (RED/WHT) wire. This circuit is known as the IGC2 circuit.
- Once the ignition coils get their IGC1 and IGC2 signals, they start to spark away.