Electronic Ignition (EI) System Diagnosis
Circuit Description

The electronic ignition system uses an individual ignition coil for each cylinder. The powertrain control module (PCM) controls the ignition operation through eight individual ignition control (IC) circuits. Each bank of four ignition coils is connected to the PCM, power, or ground by the following circuits:

* Low reference
* Chassis ground
* Ignition 1 voltage
* The appropriate IC circuit

The PCM triggers an ignition coil by grounding the appropriate IC circuit using information from the crankshaft position (CKP) and camshaft position (CMP) sensors.

Important

A missing CMP sensor signal may cause a long crank condition.

The CKP signal must be available for the engine to start. The CMP signal is not needed to start and operate the engine. The PCM can determine when a cylinder is on either the firing or exhaust stroke by the 24X signal.

Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing or replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.


Attempt to start the engine.

1. Observe the Engine Speed parameter with a scan tool.
2. Crank the engine.

Does the scan tool indicate RPM is present?

1. Turn ON the ignition, with the engine OFF.
2. Disconnect the crankshaft position (CKP) sensor.
3. Measure the voltage from the CKP sensor 12-volt reference circuit and a good ground with the Digital Multimeter.
4. Compare the measured voltage with the system voltage.

Is the difference in the voltage more than the specified value? 0.5V

 

Other items to check:

1. Disconnect the main ignition coil 8-way connector.
2. Probe the ignition 1 voltage circuit at the ignition coil main 8-way connector using the test lamp connected to battery ground.

Does the test lamp illuminate?
----------
1. Disconnect the main ignition coil 8-way connector.
2. Probe the ignition 1 voltage circuit on the harness side with a test lamp connected to the ground circuit of the ignition coil.

Does the test lamp illuminate?
----------
1. Disconnect the main ignition coil 8-way connector.
2. Probe the ignition 1 voltage circuit on the harness side with a test lamp connected to the low reference circuit of the ignition coil.

Does the test lamp illuminate?
----------
Test for a short to ground in the CKP 12-volt reference circuit or the camshaft position (CMP) sensor 12-volt reference circuit

 

It does have some BCM and Brake codes. No VTD's that I'm aware of. Like I said though, they were set when I was checking the fuses with the ignition on.

 

Anyone know how the knock sensors work? I tried to measure the resistance on a new one and got NOTHING.

 

measure them while they are installed, and just go from the wire to the sensor and a ground, repeat for the other sensor. I have never been very succesful measureing them un-installed. I miss informed you the last post, the sensors should ohm at 93-107k Ohms..sorry about that its been awhile since Ive turned wrenchs

sensors use piezo-electric crystal technology to produce and send signals to the PCM. The amplitude and frequency of this signal will vary constantly depending on the vibration level within the engine, basicly they create a voltage drop according to how much knock they are experiencing and the PCM has set ranges in its logic to calculate the spark

 

Have you cleared all of the codes....BCM,PCM and whatever else pops up and tried again? make a note of any codes that pop up again after trying to start..maybe that can help?? It sucks tryin to help over the internet and not in person...

Ok I just went and checked ....my truck WILL start with the knock sensors unplugged...it WILL NOT start with the MAP sensor unplugged though...I think we've been chasing our tails around

 

Well **** ... counts that out then. Maybe I will get a MAP sensor and try again.

2nd though ... it's working cause it's reading 100-101 at a rest and 99.9 while cranking.

 

Has anyone considered that the crank shaft has the wrong reluctor wheel?

**edit** i know they are different from year to year.

 

Get that thing towed to a mechanic with some testing equipment i.e. lab scope, scanner, and lots of books.

 

I will drive my truck to New york and back with the MAP Sensor unplugged.