The following instructions are for testing the Crank Position Sensor (CPS) and Ignition Control Module (ICM) for Reatta models '88-'90 when the engine will not start.
This tutorial is not intended to diagnose a CPS that is failing intermittently, although it might be useful for that purpose. Read this entire tutorial before attempting to perform the tests in this tutorial. Please click here and read our disclaimer before using this tutorial.
This tutorial is intended for Reatta owners who have experience in working with hand tools and are familiar with the safety practices related to working around the moving parts of an engine. All safety precautions should be strictly adhered to.
Tools Needed:
- Analog or Digital Multimeter .
- Wire piercing probe attachment for multimeter lead or long sharp pin. (see photo below)
- CPS Tester (if your digital volt meter won't detect the CPS signal)
Instructions for building a tester can be found here. - Contact cleaner for cleaning wires.
- 1-1/8" socket and ratchet.
Before you begin the tests:
- Make sure the battery is in good condition and fully charged. A low battery could affect test results.
- Clean wires at Ignition Control Module (ICM) connector and remove tape if needed to be able to see wire colors.
This tutorial requires piercing the insulation of the wires going into the ICM . Be very careful not to damage the wires. An alternate method may be used as long as you can connect the meter and tester as described in each test. If you don't feel comfortable about piercing the wires do not proceed with this tutorial. Please see the chart at the bottom of this page for references to wiring colors and designations.
The following tests should be performed in sequence.
TEST 1 - Spark
Test for spark from the coils
- Remove a spark plug wire .
- Check for a good spark while an assistant attempts to start the engine.
(The spark should be blueish white and jump at least 1/2" to ground.)
Do you have fire to the spark plugs?
YES - Stop here! The CPS or ICM is not the reason the engine will not start.
NO - Continue to TEST 2.
TEST 2 - ICM power
Test for power going to the ICM
- Make sure the key is in the OFF position.
- Pierce the first wire [P] on the left side of the ICM connector (Pink/Black stripe).
- Set multimeter to 50 volt DC range.
- Connect multimeter Red + lead to the wire (Pink/Black stripe) and the Black - lead to ground.
- Turn the key to the Run position but DO NOT try to start.
You should read 12 volts DC.
Do you read 12 volts?
YES - Continue to TEST 3.
NO - Check wiring and fuse #8 (CCCI, a 15 amp fuse) located in the center console. Then repeat TEST 2.
TEST 3 - CPS power
Test for power going to the CPS
- Make sure the key is in the OFF position.
- Pierce the second wire [N] from the left side of the ICM connector (White/Black stripe).
- Set multimeter to 50 volt DC range.
- Connect multimeter Red + lead to the wire (White/Black stripe) and the Black - lead to ground.
- Turn the key to the Run position but DO NOT try to start.
You should read 10 volts DC.
Do you read at least 10 volts DC?
YES - Continue to TEST 4.
NO - Check the ICM for a good ground between the module and the mounting plate. If ground is good replace the ICM and repeat all the above tests.
TEST 4 - 3X signal
Check the 3X CPS sync signal
WARNING!
Disconnect All spark plug wires and move them away from the coils! Make certain that no one has access to the ignition key but you! Failure to do this could result in personal injury and damage to your automobile.
- Pierce the seventh [H] wire on the left side of the bolt holding the connector to the ICM (Light Blue/White stripe).
- Connect CPS tester's Red + lead to the wire (Light Blue/White stripe) and the Black - lead to ground.
- Make certain that ALL the spark plug wires are removed from the coils. DO NOT SKIP THIS STEP!!
- Turn the key to the RUN position. Do not attempt to start the engine.
- Using a 1-1/8" socket wrench turn the crankshaft in the clockwise direction and observe the CPS tester.
- Remove the socket wrench from the engine.
The CPS tester should flash on and off.
Do you see it flash?
YES - Continue to TEST 5.
NO - Replace the CPS and repeat all the above tests.
TEST 5 - 18X signal
Check the 18X CPS signal
- Make sure the key is in the OFF position.
- Pierce the eighth [G] wire on the right side of the bolt holding the ICM connector to the ICM (Dark Blue/White stripe)..
- Connect CPS tester's Red + lead to the wire (Dark Blue/White stripe) and the Black - lead to ground.
- Make certain that ALL the spark plug wires are removed from the coils. DO NOT SKIP THIS STEP!!
- Turn the key to the RUN position. Do not attempt to start.
- Using a 1-1/8" socket wrench turn the crankshaft in the clockwise position and observe the CPS tester.
- Remove the socket wrench from the engine.
The CPS tester should flash on and off.
Do you see it flash?
YES - Test/Replace ICM and/or ECM. (Assuming all CPS tests passed.)
NO - Replace the CPS and repeat all the above tests.
Dab a tiny amount of clear silicone on each spot where you pieced the wires for the test to seal out moisture.
Wiring diagram for reference
Thanks to members of the Reatta forums for this information.
