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 PCMs microprocessor. When the output is OFF, the quad driver should receive the 12 volts fed to the solenoid, relay, etc. When the output is ON, the quad driver should receive 0 volt since it is grounding the output. If it receives 0 volt when the output is OFF or 12 volts when the output is ON, it sets the fault line low. 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. |
Diagnostic Aids
Review the Freeze Frame and Failure Records that were stored when this DTC set. Check these conditions to determine the odometer reading and driving conditions under which this DTC set.
Step | Action | Value(s) | Yes | No | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||||||||||
2 |
Does the display indicate OK? | -- | ||||||||||||||
3 | While viewing the Quad Driver 1 display, command All Relays ON. Does the display indicate OK? | -- | ||||||||||||||
4 | Is there a cooling fan operation complaint or fault suspected? | -- | Go to Electric Cooling Fan Diagnosis | Go to Diagnostic Aids | ||||||||||||
5 | While viewing the Quad Driver 1 display, command Fan Relay 1 ON. Does the display indicate OK? | -- | ||||||||||||||
6 |
Is the voltage the same or less than the value specified? | 0.5 volts | ||||||||||||||
7 |
Is the voltage the same or less than the value specified? | 0.5 volts | ||||||||||||||
8 | With All Relays still commanded OFF observe the operation of both cooling fans. Is either fan operating? | -- | ||||||||||||||
9 |
Is the voltage the same or more than the value specified? | 10.0 volts | ||||||||||||||
10 |
Is the voltage the on both terminals the same or more than the value specified? | 10.0 volts | ||||||||||||||
11 | Was the voltage measured in Step 10 low for both terminals? | -- | ||||||||||||||
12 | Repair the open circuit or replace the open fan relay for the CKT that measured low in Step 9. Is the repair complete? | -- | -- | |||||||||||||
13 |
Is the repair complete? | -- | -- | |||||||||||||
14 | Repair short to ground in CKT 473. Is the repair complete? | -- | -- | |||||||||||||
15 | Repair short to ground in CKT 335. Is the repair complete? | -- | -- | |||||||||||||
16 | Repair short to voltage in CKT 335. Is the repair complete? | -- | -- | |||||||||||||
17 | Repair short to voltage in CKT 473. Is the repair complete? | -- | -- | |||||||||||||
18 |
Was terminal contact repaired? | -- | ||||||||||||||
19 | Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the replacement complete? | -- | -- |
