Ignition System Tests

New floating point processors no longer use an EDIS chip for ignition signal processing. The crank and cam position signals are now directly processed by the PCM/ECM microprocessor using a special interface called a Time Processing Unit or TPU, or General Purpose Time Array (GPTA), depending on the PCM/ECM. The signals to fire the ignition coil drivers also come from the microprocessor.

Historically, Ford has used a 36-1 tooth wheel for crankshaft position (40-1 on a V-10). Many engines still use a 36- 1 wheel; however, some new engines are migrating to a 60-2 tooth wheel for crankshaft position. This was done to commonize ignition hardware and allow Ford to use some industry-standard PCM/ECM designs. 60-2 tooth crank wheels are being used on the 2011/2012 MY 2.0L GDI and GTDI engines, 1.6L GTDI engines and the 3.5L TIVCT GTDI engine.

Over the years, Ford ignition system have migrated away from Distributorless Ignition Systems (DIS) where a given coil pack fires two spark plugs at the same time (one spark plug fires during the compression stroke, the other spark plug fires during the exhaust stroke). All new engine now use Coil On Plug (COP) systems where there is an ignition coil and a coil driver for each spark plug, thus eliminating the need for secondary spark plug wires and improving reliability. Historically, Ford located the ignition coil drivers within the PCM/ECM, however, some new engines are migrating to coils where the driver is located on the coil itself. This eliminates the high current lines going from the PCM to the coils and again, commonizes ignition hardware to allow Ford to use some industrystandard PCM/ECM designs.

The ignition system is checked by monitoring various ignition signals during normal vehicle operation:

• CKP, the signal from the crankshaft 36-1-or 60-2 tooth wheel. The missing tooth is used to locate the cylinder pair associated with cylinder # 1 The microprocessor also generates the Profile Ignition Pickup (PIP) signal, a 50% duty cycle, square wave signal that has a rising edge at 10 deg BTDC for 36-1 systems and 12 deg BTDC for 60-2 systems.
• Camshaft Position (CMP), a signal derived from the camshaft to identify the #1 cylinder
• Coil primary current (driver in module ignition systems). The NOMI signal indicates that the primary side of the coil has achieved the nominal current required for proper firing of the spark plug. This signal is received as a digital signal from the coil drivers to the microprocessor. The coil drivers determine if the current flow to the ignition coil reaches the required current (typically 5.5 Amps for COP, 3.0 to 4.0 Amps for DIS) within a specified time period (typically > 200 microseconds for both COP and DIS).
• Coil driver circuit current and/or voltage (driver on coil ignition systems). The PCM/ECM coil driver IC checks for out of range current and voltage levels at the coil driver output that would indicate an open or short circuit fault. The fault could be located anywhere in the coil driver circuit: PCM/ECM, wiring harness, coil connector, or the driver circuit on the ignition coil. (Note this does not include the primary side windings. Faults in the primary side windings must be detected by the Misfire Monitor for driver on coil ignition systems).

First, several relationships are checked on the CKP signal. The microprocessor looks for the proper number of teeth (35 or 39 or 58) after the missing tooth is recognized; time between teeth too low (< 30 rpm or > 9, 000 rpm); or the missing tooth was not where it was expected to be. If an error occurs, the microprocessor shuts off fuel and the ignition coils and attempts to re-synchronize itself. It takes on revolution to verify the missing tooth, and another revolution to verify cylinder #1 using the CMP input. Note that if a P0320 or P0322 DTC is set on a vehicle with Electronic Throttle Control, (ETC), the ETC software will also set a P2106.

If the proper ratio of CMP events to PIP events is not being maintained (for example, 1 CMP edge for every 8 PIP edges for an 8-cylinder engine), it indicates a missing or noisy CMP signal (P0340). On applications with Variable Cam Timing (VCT), the CMP wheel has five teeth to provide the VCT system with more accurate camshaft control. The microprocessor checks the CMP signal for an intermittent signal by looking for CMP edges where they would not be expected to be. If an intermittent is detected, the VCT system is disabled and a P0344 (CMP Intermittent Bank 1) or P0349 (CMP intermittent Bank 2) is set.

Finally, for driver in module ignition systems, the relationship between NOMI events and PIP events is evaluated. If there is not an NOMI signal for every PIP edge (commanded spark event), the PCM will look for a pattern of failed NOMI events to determine which ignition coil has failed.

If an ignition coil primary circuit failure is detected for a single cylinder or coil pair, the fuel injector to that cylinder or cylinder pair will be shut off for 30 seconds to prevent catalyst damage. Up to two cylinders may be disabled at the same time on 6 and 8 cylinder engines and one cylinder is disabled on 4 cylinder engines. After 30 seconds, the injector is re-enabled. If an ignition coil primary circuit failure is again detected, (about 0.10 seconds), the fuel injector will be shut off again and the process will repeat until the fault is no longer present. Note that engine misfire can trigger the same type of fuel injector disablement.