Electronic Ignition (EI) System Diagnosis. Oldsmobile Shelby Series 1 1999

For 1990-2009 cars

Refer to Engine Controls Schematics for wiring view.

#### Circuit Description

The ignition control module (ICM) determines crankshaft and camshaft position and fires the appropriate spark plug. The ICM also creates 4X and 24X reference pulses that are supplied to the powertrain control module (PCM). The PCM uses these reference circuits to determine fuel delivery and spark timing. Most failures in the ignition control system will set a PCM diagnostic trouble code (DTC). Always perform the Powertrain On Board Diagnostic (OBD) System Check and, if necessary, the Engine Cranks but Does Not Run diagnostic table BEFORE performing any ignition system diagnsosis.

### Test Description

1. The Engine Cranks but Does Not Run table must be performed BEFORE using this diagnostic procedure.

2. Observe the Engine Speed parameter on the scan tool while increasing spark RETARD by 10 degrees. The PCM will attempt to keep the engine speed at the Desired Idle during spark retard by slightly increasing spark advance. The engine speed may initially drop by 50 RPM then increase slightly to average 30 RPM less than the RPM observed during normal spark control.

   If engine speed fails to decrease, proceed to step 4 of DTC P1350 diagnosis.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Using a scan tool, check for stored PCM diagnostic trouble codes. Are any DTCs set? | -- | Go to the DTCs | Go to Step 3
3 | Attempt to start and idle the engine. Does the engine start? | -- | Go to Step 4 | Go to Step 7

4

1. With the engine at idle, disconnect the IAC valve.
2. Using a scan tool, select Spark Retard.
3. While monitoring engine speed retard the spark timing using the scan tool.
4. Observe the engine speed as spark is retarded.

Does engine speed decrease as spark is retarded?

--

Go to Step 5

Go to DTC P1350 Ignition Control System

5

1. Reconnect the IAC valve.
2. Using the scan tool, clear any stored DTCs.
3. Turn the ignition OFF and wait 30 seconds.
4. Start and operate the vehicle and record any driveability concerns.

Is a miss, stumble, or hesitation observed?

--

Go to Secondary Ignition Diagnosis

Go to Step 6

6 | Were any other driveability symptoms observed? | -- | Go to Symptoms | System OK

7

1. Disconnect ICM connector C2.
2. Connect a test lamp between terminals A and C.

Does the test lamp illuminate?

--

Go to Step 11

Go to Step 8

8 | Connect the test lamp between terminal C and a good engine ground. Does the test lamp illuminate? | -- | Go to Step 9 | Go to Step 10
9 | Repair the open ground circuit to the IC module. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Step 12 | --

10

Repair the cause of no voltage to the ICM. Possibilities include the following:

• | An open ignition feed circuit

• | A shorted to ground ignition feed circuit or blown fuse

• | An internally shorted IC module or blown fuse

• | No voltage supply to the ICM fuse (possible blown fuse)

Is the repair complete?

--

Go to Step 12

--

11

1. Check terminal contact at the IC module.
2. Repair terminal contact if needed.

Was terminal contact repaired?

--

Go to Step 12

Go to Ignition System CKP Sensor Diagnosis

12 | Select the Capture Info option and Review Info option using the scan tool. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to the applicable DTC table | System OK