Powertrain Control Power and Ground Check. Cadillac Concours 1996

For 1990-2009 cars

## Powertrain Control Power and Ground Check 1 of 2

Engine Controls Components
PCM Power and Grounds
OBD II Symbol Description Notice
ESD Notice

### Circuit Description

The PCM is fed battery voltage at all times at PCM connector C1 terminals 20 and 61 through CKT 2240 from the Engine Compartment Fuse/Relay Center, fuse D7. IGN 1 voltage (Hot in Run, Bulb Test or Start) is fed through CKT 639 and the Engine Compartment Fuse/Relay Center, fuse C7 to PCM connector C1 terminal 19 and C2 terminal 37. IGN 0 voltage (Hot in all positions except LOCK) is fed through the Engine Compartment Fuse Block fuse A1 and CKT 147 to PCM connector C1 terminal 18. The PCM needs all of these inputs to function properly.

The PCM also has four grounding points: at terminals 21 and 60 of both PCM connectors C1 and C2. These terminals are grounded through CKT 451 to ground G102.

### Diagnostic Aids

Ensure that the battery is fully charged and tested before performing this check.

### Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

1. Checking battery power supply to the PCM.

2. Checking Ignition 0 voltage to the PCM.

3. Checking Ignition 1 and Ignition Supplement voltage to the PCM.

4. 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.

#### PCM Power and Ground Check

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain OBD System Check performed? | -- | Go to Step 2 | Go to Powertrain OBD System Check

2

1. Ensure that the battery is fully charged and tested.
2. Record the fluid life indexes, turn the key to LOCK and wait 30 seconds.
3. Disconnect PCM connectors C1 and C2.
4. Using DMM J 39200 separately measure the voltage to ground at PCM connector C1 terminals 20 and 61.

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 Engine Compartment Fuse/Relay Center fuse D7. Is fuse D7 blown? | -- | Go to Step 13 | Go to Step 14

5

1. Turn the key ON.
2. Measure the voltage to ground at PCM connector C1 terminal 18 (harness side).

Is the voltage more than the value specified?

10.0 volts

Go to Step 7

Go to Step 6

6 | Examine engine compartment fuse block fuse A1. Is the fuse blown? | -- | Go to Step 15 | Go to Step 16
7 | 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

9

1. Turn the key to LOCK.
2. Individually measure the resistance to ground at PCM connector C1 terminals 21 and 60 and C2 terminals 21 and 60 (all on harness side).

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

1. Check terminal contact at PCM connector C1 terminals 18, 19, 20, 21, 60 and 61 and PCM connector C2 terminals 21, 30, and 61.
2. Repair terminal contact as needed.

Was terminal contact repaired?

--

Go to Powertrain Control Module Diagnosis for Verify Repair

PCM Power and Ground Check OK. Go to 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 to fuse D7. Refer to Electrical Diagnosis 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 to fuse A1. Refer to Electrical Diagnosis 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 Electrical Diagnosis 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 | --

## Powertrain Control Power and Ground Check 2 of 2

### Powertrain Ground Check

Refer to Engine Controls Components for ground location views.

### Circuit Description

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 PCM Power and Ground Check (2 of 2) should be performed when referred to by other diagnostics or when erratic or intermittent problems defy traditional diagnosis. The PCM Power and Ground Check (2 of 2) table lists these grounds and other pertinent information that will allow you to investigate a possible loose or faulty ground connection.

#### Diagnostic Aids

Check the grounds listed in the Powertrain Ground Check table for the following conditions:

• | Corrosion or paint between the ring terminal and the grounding surface.

• | Poor quality crimp of the ring terminal to the ground wire.

• | damaged ground wire.

Ground | General Usage | Circuit | Location
--- | --- | --- | ---
G100 | Battery to vehicle connection. | Black | Engine Compartment
G102 | MAF sensor, EVAP vacuum switch, oil level switch, cruise control module, fuel pump relay, transaxle range switch, ign. relay, PCM. | 451 BLK/WHT | Engine Compartment
G102 | Ignition control module. | 450 Black | Engine Compartment
G109 | Heated oxygen sensors (HO2S) (All) | 250 Black | Engine Compartment
G107 | A/C compressor clutch, cooling fans. | 350 Black | Engine Compartment
G401 | Fuel pump, RSS module, rear defogger, ELC compressor, keyless entry module. | 1250 Black | Trunk Compartment