Refer to Engine Controls Schematics
PCM Power and Grounds
.
Circuit Description
The diagnostic tables in this section are designed for use with a scan tool. If the scan tool is inoperative, this condition must be corrected before beginning any other diagnostic procedures. If the scan tool being used is powered through the data link connector (DLC), the B+ power is provided by DLC Pin 16. DLC Pin 4 provides the ground for the scan tool's power supply. DLC Pin 5 is an additional ground for serial data. The serial data for the powertrain diagnostics is on DLC Pin 2.
Diagnostic Aids
Notice: Use the connector test adapter kit J 35616-A for any test that
requires probing the following items:
• The PCM harness connectors • The electrical center fuse/relay cavities • The component terminals • The component harness connector
If the problem is intermittent, refer to Intermittent Conditions .
Test Description
The numbers below refer to the step numbers on the diagnostic table:
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If the ground circuit on the DLC pin 4 opens after the scan tool is up and running, the screen may go blank with the scan tool remaining on. If there is no ground at pin 4 initially, the scan tool will not power up.
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Some of the older scan tools are powered through a separate power cord from the cigar lighter. If this type of scan tool is being used, and the tool will not power up, check for a poor connection, or a malfunctioning lighter socket. Refer to Testing for Intermittent and Poor Connections in Wiring Systems.
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If there is no communication between the PCM and the scan tool, no data will be displayed. The serial data is disrupted when the system voltage is below 9.0 volts or more than 16.0 volts. A scan tool will not display data if the system voltage is outside of this range. If data is displayed with the ignition on and the engine off, but data is lost when the engine is running, high system voltage (overcharging) may be at fault. If this is the case, the scan tool should display DTC P0560 System Voltage with the ignition on and the engine off.
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Try the scan tool on another vehicle if one is available. An alternate approach is to try a different scan tool on the same vehicle, if one is available. Before trying a different scan tool, check for poor connections between the DLC and the scan tool cable. Refer to Testing for Intermittent and Poor Connections in Wiring Systems.
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Before trying a different scan tool, check for poor connections between the DLC and the scan tool cable. Refer to Testing for Intermittent and Poor Connections in Wiring Systems.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
Is the scan tool powered up? | -- | |||
3 | Does the scan tool communicate with any systems other than the PCM, such as the antilock brake system (ABS), or the heating, ventilation, and air conditioning (HVAC) system? | -- | Go to Diagnostic Starting Point for serial data circuit diagnosis | |
4 | Does the engine start and run? | -- | ||
5 |
Does the test lamp illuminate on all circuits? | -- | ||
6 | Measure resistance on the PCM ground circuits in the PCM harness connector C1 with digital multimeter (DMM) J 39200 connected to battery ground. Does the DMM indicate the value shown or lower? | 5 ohms | ||
7 | Repair the affected power feed circuit. Is the action complete? | -- | -- | |
8 | Repair the open or high resistance in the affected ground circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
Does the test lamp illuminate? | -- | |||
10 | Measure resistance on DLC terminal 4 and terminal 5 with a DMM J 39200 connected to the battery ground. Does the DMM indicate the value shown or lower on both circuits? | 5 ohms | ||
11 | Repair the B+ circuit to DLC terminal 16. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check
| -- |
Check the Serial Data circuit to DLC Pin 2 for an open between the PCM and the splice. Refer to Diagnostic Starting Point . Was a problem found and corrected? | -- | |||
13 | Repair the open or high resistance ground circuit to the DLC. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
Verify the scan tool operation on another vehicle. Refer to the Test Description. . Does the scan tool display data? | -- | |||
15 | Check for poor connections and terminal tension at the PCM harness connector. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Was a problem found and corrected? | -- | ||
16 |
Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | |
The scan tool may be malfunctioning. Use a different scan tool if one is available. Refer to the Test Description. . Is the action complete? | -- | -- |
