Refer to Engine Controls Schematics for wiring view.
Circuit Description
The PCM contains a chip called a Quad Driver Module that provides 4 switchable ground outputs for operating solenoids, relays, telltales, and other devices. Each of these ground outputs has an internal fault line that feeds back to the PCM's microprocessor. When the output is OFF, the quad driver should sense the 12 volts fed to the solenoid, relay, etc. When the output is ON, the ouad driver should sense 0 volt since it is grounding the output. If the PCM senses 0 volt when the output is OFF or 12 volts when the output is ON, the PCM sets DTC P1660. DTC P1660 is used to monitor the fault line of the cooling fan control relay output.
Conditions for Running the DTC
| • | Ignition voltage between 10 and 16 volts. |
| • | PCM in Closed Loop fuel control. |
| • | Engine running for at least 10 seconds. |
Conditions for Setting the DTC
Fault line is low for 2 seconds.
Action Taken When the DTC Sets
| • | The PCM will illuminate the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails. |
| • | The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail. |
| • | A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail. |
| • | A History DTC will clear after forty consecutive warm-up cycles with no failures of any emission related diagnostic test. |
| • | Use a scan tool to clear DTCs. |
| • | Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in PCM Description and Operation. |
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | |
2 |
Does the display indicate OK? | -- | Go to Step 3 | Go to Step 6 |
3 | While viewing the Driver 1 display, command the Low Speed Relay ON. Does the display indicate OK? | -- | Go to Step 4 | Go to Step 8 |
4 |
Does the display indicate OK? | -- | Go to Step 5 | Go to Step 9 |
5 | Is there a cooling fan operation complaint or fault suspected? | -- | Fault not present. Go to Diagnostic Aids | |
6 |
Is the voltage the same or more than the value specified? | 10.5 - 15 volts | Go to Step 7 | Go to Step 11 |
7 | Using DMM measure the voltage to ground at PCM terminals 33. Is the voltage the same or more than the value specified? | 10.5 - 15 volts | Go to Step 14 | Go to Step 10 |
8 |
Is the voltage the same or less than the value specified? | 0.5 volts | Go to Step 14 | Go to Step 12 |
9 |
Is the voltage the same or less than the value specified? | 0.5 volts | Go to Step 14 | Go to Step 13 |
10 | Repair open, short to ground, open relay, or blown fuse in CKT 473. Is the repair complete? | -- | -- | |
11 | Repair open, short to ground, open relay, or blown fuse in CKT 335. Is the repair complete? | -- | -- | |
12 | Repair short to voltage in CKT 335. Is the repair complete? | -- | -- | |
13 | Repair short to voltage in CKT 473. Is the repair complete? | -- | -- | |
14 |
Was terminal contact repaired? | -- | Go to Step 15 | |
15 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the replacement complete? | -- | -- |
