GM Service Manual Online
For 1990-2009 cars only

Circuit Description

This engine is equipped with a distributor-less 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 module (ICM) 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

Test/Inspect for the following conditions:

    • Collapsed air intake duct.
    • Restricted air filter element. Refer to Air Cleaner Element Replacement .
    • A TP sensor that reads too high or skewed may cause an incorrect fueling condition.
    • A throttle position (TP) sensor binding or sticking in wide open position.
    • A TP sensor shorted or open.
    • Fuel contamination
    • Out of fuel
    • Restricted exhaust system. Refer to Restricted Exhaust in Engine Exhaust.
    • Low compression -- refer to Engine Compression Test in Engine Mechanical.
    • A cold engine that has not been started should display engine coolant temperature (ECT) and intake air temperature (IAT) temperatures that are relatively close to each other.
    • A skewed manifold absolute pressure (MAP) sensor. The MAP sensor value should change when cranking the engine. Compare any questionable barometer readings with that of a known good vehicle.

Check for intermittent conditions. Refer to Intermittent Conditions .

Test Description

The number below refers to the step number on the diagnostic table.

  1. While cranking the engine, the crankshaft position (CKP) activity (CKP reference signal) should increment to 255, then rollover to 0.

Step

Action

Values

Yes

No

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

  1. Turn ON the ignition, with the engine OFF.
  2. With a scan tool, observe the DTC information.

Does the scan tool display DTCs P0336, P0601, P0602, P1621, P1626, P1631, or P1632.

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3

With the scan tool, observe the CKP activity counter while cranking the engine.

Does the CKP activity counter increment while cranking the engine?

--

Go to Step 4

Go to Electronic Ignition (EI) System Diagnosis

4

  1. Turn ON the ignition, with the engine OFF.
  2. Important: Ensure the fuses below are not open, before proceeding with this test.

  3. Probe both sides of the following fuses with a test lamp to ground:
  4. • ECM B
    • ECM 1
    • CLSTR Fuse 11
    • TBC

Does the test lamp illuminate on both sides of all the fuses?

--

Go to Step 5

Go to Testing for Short to Ground in Wiring Systems

5

With the scan tool, command the fuel pump ON.

Does the fuel pump run?

--

Go to Step 6

Go to Fuel Pump Electrical Circuit Diagnosis

6

  1. Turn OFF the ignition.
  2. Install a fuel gauge. Refer to Fuel Pressure Gage Installation and Removal .
  3. Turn ON the ignition, with the engine OFF.

Does the fuel pressure read within the specified value?

248-325 kPa

(41-47 psi)

Go to Step 7

Go to Fuel System Diagnosis

7

  1. Turn OFF the ignition.
  2. Disconnect a fuel injector connector.
  3. Install a fuel injector test lamp into the connector.
  4. Crank the engine.

Does the test lamp blink while cranking the engine?

--

Go to Step 8

Go to Fuel Injector Circuit Diagnosis

8

  1. Install a J 26792 Spark Tester on #1 spark plug wire leaving the other wires connected.
  2. Crank the engine while observing the spark tester.
  3. Repeat the procedure on the remaining cylinders.

Did spark occur on all cylinders?

--

Go to Step 9

Go to Electronic Ignition (EI) System Diagnosis

9

  1. Turn OFF the ignition.
  2. Inspect for malfunctioning spark plugs. Refer to Spark Plug Inspection .

Did you find and correct the condition?

--

Go to Step 10

Go to Diagnostic Aids

10

Attempt to start the engine.

Does the engine start and continue to run?

--

Go to Diagnostic System Check - Engine Controls

Go to Step 2