| Table 1: | PCM Power and Ground Check |
| Table 2: | Powertrain Ground Check |
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 2240 from the 10 amp fuse. IGN 1 voltage ,Hot in Run or Start, is fed through CKT 639 and fuse C7 to PCM connector C1 terminal 19 and C2 terminal 37. IGN 0 voltage (Hot in all positions except LOCK) is fed through fuse A1 to PCM connector C1 terminal 18. 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 G102.
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
Number(s) below refer to the step number(s) on the Diagnostic Table.
-
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 | Did you perform the Powertrain On-Board Diagnostic System Check? | -- | ||
Is the voltage more than the value specified on both terminals? | 10.0 volts | |||
3 | Does only one terminal measure more than the value specified? | 10.0 volts | ||
4 | Examine Engine Compartment Fuse/Relay Center fuse D7. Is fuse D7 blown? | -- | ||
5 |
Is the voltage more than the value specified? | 10.0 volts | ||
6 | Examine engine compartment fuse block fuse A1. Is the fuse blown? | -- | ||
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 | |||
8 | Does only one terminal measure more than the value specified? | 10.0 volts | ||
Is the resistance measured less than the value specified on all terminals? | 5 ohms | |||
10 | Did all of the terminals measure more than the value specified? | 5 ohms | ||
11 |
Was terminal contact repaired? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | Perform Powertrain Ground Check |
12 | Repair the open in CKT 2240 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 2240 and replace fuse D7. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
14 | Repair the open in both CKT 2240s or the cause of no voltage supply to fuse D7. Refer to Wiring Systems 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 147 and replace fuse A1. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
16 | Repair the open in CKT 147 or the cause of no voltage supply to fuse A1. Refer to Wiring Systems 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 639 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 639 and replace fuse C7 or repair the cause of no voltage supply to the fuse. Refer to Wiring Systems 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 G102 or the G102 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 |
|---|---|---|---|
G100 | Battery to vehicle connection. | Black | Engine Compartment |
G102 | MAF Sensor, Oil Level sensor, Fuel Pump relay, PNP switch, PCM. Heated Oxygen Sensors (HO2S) (All) | 451 BLK/WHT | Engine Compartment |
G102 | Ignition Control module. | 450 Black | Engine Compartment |
G107 | A/C compressor clutch, cooling fans. | 350 black | Engine Compartment |
G401 | Fuel Pump, rear defogger, ELC compressor, etc. | 1250 Black | Trunk Compartment |
