GM Service Manual Online
For 1990-2009 cars only

Object Number: 21631  Size: LF
Engine Controls Components
Ignition System
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

Description

This table assumes that battery condition and engine cranking speed are OK. If not, refer to Engine Electrical for diagnosis. Also, make sure that there is adequate fuel in the tank.

Diagnostic Aids

    • An EGR valve sticking open can cause a low air/fuel ratio during cranking.
    • Unless the engine enters Clear Flood at the first indication of a flooding condition, a no start may result.
    • Check the duct work between the Mass Air Flow (MAF) sensor and the throttle body for air leaks.
    • A malfunctioning MAF sensor may cause a no start or a stall after start. If this is suspected, disconnect the MAF sensor. The PCM will default to speed density (MAP, IAT, RPM) to calculate load and air flow. If this corrects the condition and the connections are OK, replace the MAF sensor.

If the steps above check OK, refer to Symptoms .

Test Description

Number(s) below refer to step numbers on the diagnostic table.

  1. If no RPM was indicated on the scan tool during cranking, the power and ground to the distributor from the PCM are both OK, and DTC P1371-DI Low Resolution Circuit is not set, Replace the PCM.

Step

Action

Value(s)

Yes

No

1

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

Important: An open ignition feed to the injector circuit will cause the engine not to start. Inspect the injector fuse for being open. Also inspect the circuits for opens or grounds.

Using the scan tool, select ENG DTC, DTC Info, LAST TST FAIL.

Are any of the following DTCs displayed:

P0100, P0200, P0601, P0602, P1351, P1361, P1371?

--

Go to the applicable DTC table

Go to Step 3

3

Using the scan tool, check Pass Key status.

Does the scan tool indicate OK?

--

Go to Step 4

Go to Theft Deterrent System

4

Using the scan tool, check Eng Cool Temp.

Is the Eng Cool Temp on the scan tool should be close to the actual engine temperature?

--

Go to Step 5

Go to DTC P0118 Engine Coolant Temperature (ECT) Sensor Circuit High Voltage

5

Using the scan tool, check Throttle Angle at a closed throttle.

Is the Throttle Angle at the specified value?

0%

Go to Step 6

Go to DTC P0122 Throttle Position (TP) Sensor Circuit Low Voltage

6

Using the scan tool, check the Engine Speed while cranking the engine.

Is RPM indicated on the scan tool?

--

Go to Step 7

Go to Step 11

7

Using Spark Tester J 26792 (ST-125), check for spark while cranking the engine (check 2 wires).

Is spark present?

--

Go to Step 8

Basic ignition problem. Go to Distributor Ignition (DI) System Check

8

Using the scan tool, enable the fuel pump.

Does the fuel pump operate?

--

Go to Step 9

Go to Fuel Pump Electrical Circuit Diagnosis

9

  1. Turn the ignition OFF.
  2. Install a fuel pressure gauge and note the fuel pressure.
  3. Turn the ignition ON.

Is the fuel pressure within the specified range?

283-325 kPa (41-47 psi)

Go to Step 10

Go to Fuel System Diagnosis

10

Perform the following additional checks:

    • An EGR valve sticking open can cause a low air/fuel ratio during cranking.
    • Unless the engine enters Clear Flood at the first indication of a flooding condition, a no start may result.
    • Check the duct work between the Mass Air Flow (MAF) sensor and the throttle body for air leaks.
    • A malfunctioning MAF sensor may cause a no start or a stall after start. If this is suspected, disconnect the MAF sensor. The PCM will default to speed density (MAP, IAT, RPM) to calculate load and air flow. If this corrects the condition and the connections are OK, replace the MAF sensor.

Was a problem found and corrected?

--

Go to Step 21

Go to Hard Start for diagnosis.

11

  1. Turn the ignition OFF.
  2. Disconnect the distributor electrical connector.
  3. Turn the ignition ON.
  4. Probe terminal C of the harness connector with a test light to ground.

Does the test light illuminate?

--

Go to Step 12

Go to Step 13

12

Using DVM J 39200 measure resistance from harness connector terminal D to ground.

Does the DVM display the specified value (or lower)?

5 ohms

Go to Step 21

Go to Step 15

13

  1. Turn the ignition OFF.
  2. Disconnect the PCM connector C2.
  3. Using DVM J 39200, check continuity of the ignition feed circuit from the distributor connector to the PCM connector.

Does the DVM display the specified value (or lower)?

5 ohms

Go to Step 14

Go to Step 16

14

Using DVM J 39200, measure the resistance from the distributor connector terminal C to ground.

Does the DVM display infinite resistance?

--

Go to Step 20

Go to Step 17

15

  1. Turn the ignition OFF.
  2. Disconnect the PCM connector C2.
  3. Using DVM J 39200, check the continuity of the distributor reference low signal circuit from the distributor connector to the PCM connector.

Does the DVM display the specified value (or lower)?

5 ohms

Go to Step 20

Go to Step 18

16

Repair the open ignition feed circuit to the distributor.

Is the action complete?

--

Go to Step 22

--

17

Repair the short to ground in the ignition feed circuit to the distributor.

Is the action complete?

--

Go to Step 22

--

18

Repair the distributor reference low circuit (ground).

Is the action complete?

--

Go to Step 22

--

19

Replace the distributor. Refer to Ignition System.

Is the action complete?

--

Go to Step 22

--

20

Check the connections at the PCM.

Was a problem found and corrected?

--

Go to Step 22

Go to Step 21

21

Important:: Replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming .

Replace the PCM.

Is the action complete?

--

Go to Step 22

--

22

  1. Using the scan tool, select DTC, Clear Info.
  2. Attempt to start the engine.

Does the engine start and continue to run?

--

Go to Step 23

Go to Step 2

23

  1. Allow engine to idle until normal operating temperature is reached.
  2. Select DTC, Fail This Ign.

Are any DTCs displayed?

--

Go to the applicable DTC table

Go to Step 24

24

Using the scan tool, select Capture Info, Review Info.

Are any DTCs displayed that have not been diagnosed?

--

Go to the applicable DTC table

System OK