With Powertrain Control Module (PCM)
WITH 4L60-E AUTOMATIC TRANSMISSIONON-BOARD DIAGNOSTICS
The Powertrain Control Module (PCM) is equipped with a self diagnostic feature that detects system failures and aids the technician in locating a faulty circuit. The PCM has memory for comparing the various input information to programmed information. These conditions are described of each Diagnostic Trouble Code (DTC) chart. If a value is not within the PCM parameters, a DTC will set and default values may be used.
The PCM will continually perform a self diagnosis check. The PCM can be requested to display any stored DTC(s) by using a scan tool or manually grounding the diagnostic test terminal. When the diagnostic test terminal of the Data Link Connector (DLC) is grounded, the PCM will check the engine speed circuit input, if the voltage is zero, the PCM will flash DTC 12 and any other DTC(s) stored. If DTC 12 will not flash, refer to CHART A-1 or CHART A-2 in Computers and Control Systems / System Diagnosis / Diagnostic Charts. Testing and Inspection
NOTE: Always refer to the On-Board Diagnosis (OBD) System Check before proceeding to diagnose any system or single component. Testing and Inspection
DISPLAYING DTC(S)
The scan tool will display all stored DTC(s) in current or history status. A DTC 12 is not a fault condition with the ignition "ON," engine "OFF." When the manual grounding procedure is used, the MIL will flash all DTC(s) stored in the PCM memory (current and history). The DTC charts assume the DTC is in current status. If the DTC is in history status, the fault may be an intermittent. An "intermittent" DTC is one which will not reset during the current ignition cycle. The text of a DTC chart will contain "DIAGNOSTIC AIDS" to help locate intermittent conditions.
If a visual (physical) check does not locate the cause of the fault, J 39200 DVM can be used to test the suspected circuit. The J 39200 DVM can be used to check for opens or shorts:
SHORT TO VOLTAGE
Connect J 39200 to a known good ground on the DC voltage scale.
SHORT TO GROUND
Connect J 39200 to a known good B+ on the DC voltage scale.
OPEN CIRCUIT
Connect J 39200 to each end of the circuit on the ohms scale with voltage removed from the circuit.
PCM INTERMITTENT DIAGNOSTIC TROUBLE CODES OR PERFORMANCE
The DTC charts determine if there is a fault within the circuit. The fault must be present to locate the problem. If an intermittent condition occurs, a DTC will be stored in history status, but the circuit check will indicate a normal condition. Most intermittent conditions are usually a faulty connection or component. When diagnosing intermittents, thoroughly check the suspected circuit for:
- Poor terminal tension.
- Poor seating of connector halves.
- Poor terminal to wire connection.
- Improperly formed or damaged terminals.
- Improperly installed electrical options.
- Faulty PCM power or ground connection.
- Intermittent short or open.
- Electrical system surges caused by a defective relay, solenoid, or switch. Normally these conditions will occur when the faulty component is operated.
CLEARING HISTORY DTC(s)
All history DTC(s) can be cleared after all repairs have been completed in the following ways:
1. With a scan tool.
2. By removing voltage from the PCM.
3. Fifty ignition cycles with fault removed.