| Table 1: | PCM Power and Ground Check |
| Table 2: | Powertrain Ground Check |
Refer to Engine Controls Schematics for wiring view.
Circuit Description
PCM Power and Ground
The PCM is fed battery voltage at all times at PCM connector C1 terminals 20 and 61 through CKT 1642 from the 20 amp fuse. IGN 1 voltage ,Hot in Run, Bulb Test or Start, is fed through CKT 439 and 10 amp fuse to PCM connector C1 terminals 18 and 19 and C2 terminal 37. The PCM needs all of these inputs to function properly. The PCM also has four grounding pins: at terminals 21 and 60 of both PCM connectors C1 and C2. These terminals are grounded through CKT 451 to ground G101.
Powertrain Ground Check
There are several vehicle grounds that are essential for proper powertrain system operation. Loose or poor ground connections may cause widely varying problems, from flickering telltales to PCM DTCs to driveability problems. The Powertrain Ground Check should be performed when referred to by other diagnostics or when erratic or intermittent problems defy traditional diagnosis. The Powertrain Ground Check table lists these grounds and other pertinent information that will allow you to investigate a possible loose or faulty ground connection.
Diagnostic Aids
Ensure that the battery is fully charged and tested before performing these checks.
Test Description
The numbers below refer to the step numbers on the Diagnostic Table.
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Checking battery power supply to the PCM.
If voltage is OK, repeat this step with a test lamp to verify the circuit has good connections that will flow adequate current.
-
Checking Ignition 1 and Ignition Supplement voltage to the PCM.
If voltage is OK, repeat this step with a test lamp to verify the circuit has good connections that will flow adequate current.
-
Checking ground supply to the PCM. If PCM grounds are good, perform the Powertrain Ground Check to diagnose other vehicle grounds that may cause driveability complaints.
If resistance is OK, check the ground circuits with a test lamp to battery voltage. This will verify the circuit has good connections that will flow adequate current.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Didyou perform the Powertrain On-Board Diagnostic System Check? | -- | Go to Step 2 | |
Is the voltage more than the value specified on both terminals? | 10.0 volts | Go to Step 5 | Go to Step 3 | |
3 | Does only one terminal measure more than the value specified? | 10.0 volts | Go to Step 12 | Go to Step 4 |
4 | Examine the PCM/VATS fuse. Is the fuse blown? | -- | Go to Step 13 | Go to Step 14 |
5 |
Is the voltage more than the value specified? | 10.0 volts | Go to Step 7 | Go to Step 6 |
6 | Examine the PCM fuse. Is the fuse blown? | -- | Go to Step 15 | Go to Step 16 |
With the key ON, measure the voltage to ground at PCM connector C1 terminal 19 (harness side) and C2 terminal 37 (harness side). Is the voltage more than the value specified on both terminals? | 10.0 volts | Go to Step 9 | Go to Step 8 | |
8 | Does only one terminal measure more than the value specified? | 10.0 volts | Go to Step 17 | Go to Step 18 |
Is the resistance measured less than the value specified on all terminals? | 5 ohms | Go to Step 11 | Go to Step 10 | |
10 | Did all of the terminals measure more than the value specified? | 5 ohms | Go to Step 19 | Go to Step 20 |
11 |
Was terminal contact repaired? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | Perform Powertrain Ground Check |
12 | Repair the open in CKT 1642 that measured less than the value specified. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
13 | Repair the short to ground in either CKT 1642 and replace the PCM fuse . Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
14 | Repair the open in circuit 1642 or the cause of no voltage supply to the PCM fuse. Refer to Engine Electrical for repair of the fuse voltage supply. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
15 | Repair the short to ground in CKT 439 and replace the PCM fuse. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
16 | Repair the open in CKT 439 or the cause of no voltage supply to the PCM fuse. Refer to Engine Electrical for repair of the fuse voltage supply. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
17 | Repair the open in the CKT 439 that measured less than the value specified. Is the repair complete? | 10.0 volts | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
18 | Repair the short to ground in either CKT 439 and replace fuse C7 or repair the loss of voltage supply to the fuse. Refer to Engine Electrical for repair of the fuse voltage supply. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
19 | Repair the open in CKT 451 between the splice and G101 or the G101 connection. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
20 | Repair the open in CKT 451 between the PCM connector and the splice on the circuit(s) that measured more than the resistance specified. Is the repair complete? | 5 ohms | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
Ground | General Usage | Circuit | Location |
|---|---|---|---|
G301 | Battery to vehicle connection. | Black | Passenger compartment |
G101 | MAF Sensor, Oil Level sensor, Fuel Pump relay, PNP switch, A/C High Pressure switch, PCM. | 451 BLK/WHT | Engine Compartment |
G101 | Ignition Control module. | 1451 BLK/WHT | Engine Compartment |
G103 | Heated Oxygen Sensors (HO2S) (All) | 1350 Black | Engine Compartment |
G103 | A/C Compressor clutch, Cooling Fans. | 1350 Black | Engine Compartment |
G302 | Fuel Pump. | 1050 Black | Passenger Compartment |
