Ignition System Test
Step 7 - If the ignition coil has no trigger pulse input the
primary ignition system has failed. This system contains a crankshaft position sensor
(CKP), camshaft position sensor (CAS) which is a low voltage generating system (1.5
to 3.0 volts) and is then amplified to 12 volts by using a ignition module (amplifier)
and then transferred to the primary side of the ignition coil. The PCM (powertrain
control module) controls the engine ignition timing by advancing and retarding the
primary trigger signal to the ignition module. You might say " if the crankshaft
position sensor (CKP), camshaft position sensor (CAS) has failed wont it produce
a diagnostic trouble code?" the answer is "not always" this is because some computer
systems think the starter has failed or you have left the car in a drive gear or
the clutch not depressed completely, not allowing the engine to crank over.In this
case the computer just thinks the engine is not cranking over, even though it is.
First turn the key to the on position, with the ignition coil connected to its wiring.
Then, using a test light or a voltage multi meter ground one side of the test light
or meter and test the coil terminals, there should be power on both sides of the
coil. If the coil doesn't have power, locate the main computer system control relay
and replace it with a new unit and re-test. If 12 volts is present continue to the
next step.
Step 8 - Locate the crankshaft position sensor (CKP) and camshaft
position sensor (CAS) (note: if your engine is designed with a distributor sometimes
the CAS is inside the distributor housing) disconnect the wiring connector to probe
the connector, there are three wires on most of these sensors so three tests are
needed. Set your multi meter to ac voltage and probe any two wires on the sensor
side, have a helper crank the engine over you should observe the multi meter jumping
between 0 and 2.5 volts on two of the three combinations. Continue testing until
three pairs of wires are complete. (i.e.: right outer and center, left outer and
center and right and left wires) if no pulse is present remove the sensor and observe
inside the mounting port with a flash light. While looking inside the port have
a help crank the engine over, you should see a small hole or magnet used to trigger
the sensor, if this trigger is present replace the sensor. Perform this test for
both sensors if equipped, if the sensors test ok suspect the ignition module (amplifier)
or PCM.
(Note: try disconnecting various sensors like oxygen and coolant temperature and retest, sometimes a sensor can short circuit locking up the PCM-powertrain control module. If ignition pulse is restored plug sensor in one at a time until ignition pulse is lost, replace that sensor with new and reassemble.) Related Inspections Engine cranks but won't start - For an engine to run, you need three things to happen inside the engine, compression, fuel and ignition, without any one of these components the engine will not run. Rapid clicking sound when cranking - The starter is designed to operate on a high amperage 12 volt system, when a starter is subjected to low voltage or amperage (flow) it will cause the starter to engage and disengage rapidly producing the rapid clicking sound. To fix this problem a battery inspection or replacement is needed. There are two reasons that a battery will not perform as it should, either the alternator has failed allowing the batteries state of charge to become weak or the battery has failed and replacement is required. Unfortunately to check the alternator the engine must be running, so you must either jump start your car or replace the battery to check the charging system. If the alternator output test is ok then the battery is bad and must be replaced. If while driving the charge light indicator on the dash was not illuminated and the battery is more than three years old the battery has probably failed.
Engine stalls at idle - At idle your engine produces the least amount of emissions than in any other time it is operation. Engine idle is necessary for proper vehicle operation; it allows the engine to operate at the lowest RPM level possible without your foot on the gas pedal. Before we start we need to know one of two things is the engine running poorly causing the engine to stall at idle or is the engine running fine and it's just the idle condition that is the problem. If further assistance is needed, our certified car repair technicians are ready to answer your car questions. Related Car Repair Information
(Note: try disconnecting various sensors like oxygen and coolant temperature and retest, sometimes a sensor can short circuit locking up the PCM-powertrain control module. If ignition pulse is restored plug sensor in one at a time until ignition pulse is lost, replace that sensor with new and reassemble.) Related Inspections Engine cranks but won't start - For an engine to run, you need three things to happen inside the engine, compression, fuel and ignition, without any one of these components the engine will not run. Rapid clicking sound when cranking - The starter is designed to operate on a high amperage 12 volt system, when a starter is subjected to low voltage or amperage (flow) it will cause the starter to engage and disengage rapidly producing the rapid clicking sound. To fix this problem a battery inspection or replacement is needed. There are two reasons that a battery will not perform as it should, either the alternator has failed allowing the batteries state of charge to become weak or the battery has failed and replacement is required. Unfortunately to check the alternator the engine must be running, so you must either jump start your car or replace the battery to check the charging system. If the alternator output test is ok then the battery is bad and must be replaced. If while driving the charge light indicator on the dash was not illuminated and the battery is more than three years old the battery has probably failed.
Engine stalls at idle - At idle your engine produces the least amount of emissions than in any other time it is operation. Engine idle is necessary for proper vehicle operation; it allows the engine to operate at the lowest RPM level possible without your foot on the gas pedal. Before we start we need to know one of two things is the engine running poorly causing the engine to stall at idle or is the engine running fine and it's just the idle condition that is the problem. If further assistance is needed, our certified car repair technicians are ready to answer your car questions. Related Car Repair Information