Electronic Ignition (EI) System Diagnosis. GMC Truck Sonoma Pickup

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2000 🢒 Sonoma Pickup - 2WD 🢒 Body and Accessories 🢒 Wiring Systems 🢒 Electronic Ignition (EI) System Diagnosis

Circuit Description

This engine is equipped with a distributorless ignition system called the electronic ignition (EI) system. The primary circuit of the EI system consists of 2 separate ignition coils, an electronic ignition control (IC) module and a crankshaft position (CKP) sensor as well as the related connecting wires and the ignition control (IC) portion of the powertrain control module (PCM). Each secondary circuit consists of the secondary winding of the coil, spark plug wires and the spark plugs.

Important: The camshaft position (CMP) sensor is only used for a misfire detection and is not part of the ignition system.

Diagnostic Aids

•	A small amount of resistance in the battery positive voltage circuit to the PCM may cause a no start. Test the battery positive voltage circuit for excessive resistance or corrosion. Refer to Wiring Repairs .

•	The PCM grounds will cause a NO START only if ALL of them are not making a good connection. Refer to Wiring Repairs .

•	If the CKP sensor is loose it may cause an intermitted NO START by moving away from the reluctor wheel. Inspect the sensor and matting surface for being clean and tight.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

Repair the cause of the malfunctioning spark plugs before replacing.

Inspect for basic engine malfunction like low compression, burnt valves, a worn timing chain and worn gears, etc.

Any time the CKP sensor is removed the Crankshaft Position System Variation Learn Procedure must be performed.

The replacement PCM must be reprogrammed and the Crankshaft Position System Variation Learn procedure must be performed.

Electronic Ignition Diagnosis

Step

Action

Value(s)

Yes

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

Were any DTCs set?

Go to applicable DTC table

Go to Step 3

Crank the engine.
Observe the CKP activity counter on the scan tool.

Does the CKP activity counter increment?

Go to Step 4

Go to Step 7

Remove the fuel pump relay.
Install the spark tester on cylinder #1.
Leave the other three ignition wires connected.
Crank the engine and observe the spark tester for spark.
Repeat the procedure on cylinders #2, #3, and #4.

Do all of the cylinders have spark?

Go to Step 5

Go to Step 11

Turn OFF the ignition.
Inspect for fouled or damaged spark plugs. Refer to Spark Plug Visual Diagnosis in Engine Electrical.
If a condition is found, repair the condition as necessary.

Did you find and correct the condition?

Go to Step 22

Go to Step 6

Inspect for basic engine problems. Refer to Base Engine Misfire Diagnosis in Engine Mechanical.

Did you find and correct any conditions?

Go to Step 22

Go to Diagnostic Aids

Turn OFF the ignition.
Disconnect the ICM 2 pin connector.
Turn ON the ignition, with the engine OFF.
Connect a DMM between the ICM ground circuit and the ICM ignition 1 voltage circuit at the connector.

Does the voltage measure the specified value?

B+

Go to Step 8

Go to Step 17

Disconnect the ICM 6 pin connector.
Measure the resistance between the CKP sensor signal circuit and the CKP low reference circuit at the connector.

Does the resistance measure within the specified value?

700-1,300 ohms

Go to Step 9

Go to Step 12

With the DMM still connected and set to AC scale.
Crank the engine and observe the DMM.

Does the voltage measure more than the specified value?

200 mV

Go to Step 10

Go to Step 18

Connect a test lamp to battery voltage.
Momentarily touch the test lamp to the CKP sensor signal circuit, then touch the low reference circuit.
Observe the CKP activity counter on the scan tool.

Does the CKP activity counter increment?

Go to Step 13

Go to Step 15

Turn OFF the ignition.
Disconnect the PCM connectors.
Connect the spark tester to the spark plug wire that did not spark.
Turn ON the ignition.
Connect a test lamp to battery voltage and momentarily touch the affected IC circuit at the PCM connector with the test lamp.

Does the spark tester spark?

Go to Step 14

Go to Step 16

Inspect/test the CKP sensor signal circuit for the following conditions:

•	A faulty connection

•	An open circuit

•	A short to ground

•	A short to voltage

If a condition is found, repair the condition as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 22

Go to Step 18

Inspect for faulty connections at the ICM. Refer to in Wiring Systems.
If a condition is found, repair the condition as necessary. Refer to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 22

Go to Step 19

Inspect for faulty connections at the PCM. Refer to Wiring Repairs in Wiring Systems.
If a condition is found, repair the condition as necessary. Refer to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 22

Go to Step 21

Inspect/test the CKP sensor signal circuit for the following conditions:

•	A faulty connection

•

An open

•	A short to ground

•	A short to voltage

If a condition is found, repair the condition as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 22

Go to Step 21

Test the affected ignition control circuit for an open or a short.
If a condition is found, repair the condition as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 22

Go to Step 20

Repair the open in the B+ supply and/or ground circuit.

Did you complete the repair?

Go to Step 22

Replace the CKP sensor. Refer to Ignition Control Module Replacement .

Did you complete the replacement?

Go to Step 22

Replace the ICM. Refer to Ignition Control Module Replacement .

Did you complete the replacement?

Go to Step 22