DTC P1645 Evaporative Emission (EVAP) Purge Solenoid Control Circuit. Cadillac Concours 1997

For 1990-2009 cars
Engine Controls Components
MAF Sensor/ EVAP Components/ Linear EGR Valve
OBD II Symbol Description Notice
ESD Notice

### Circuit Description

The PCM contains chips called Output Driver Modules that provide 7 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 output driver should receive the 12 volts fed to the solenoid, relay, etc. When the output is ON, it 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 P1645 is used to monitor the fault line of the EVAP purge solenoid.

### Conditions for Setting the DTC

#### Test Conditions

• | DTC P1640 not set.

• | Engine running at least 10 seconds.

#### Failure Condition

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

Notice: Do not apply voltage to the EVAP vacuum switch. The voltage supplied by the PCM is of a low current design. The EVAP vacuum switch may be damaged if jumpered to voltage without this current limiting feature.

Use the Failure Rec. to aid in diagnosing an intermittent fault. Use the data captured when the DTC set to determine if an open or shorted condition caused the DTC to set.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to A Powertrain On Board Diagnostic (OBD) System Check
2 | Are DTCs P1633 or P1644 also set? | -- | Go to diagnosis for the DTC that is set | Go to Step 3
3 | Are DTCs P0102, P0401, P0550, P0753, P0758, P1406 or P1860 also set? | -- | Go to Step 10 | Go to Step 4
4 | Using a scan tool view the EVAP Sol. Driver display. Does the display indicate OK? | -- | Go to Step 5 | Go to Step 6

5

1. Start and idle the engine.
2. In Output Tests select EVAP Purge.
3. Command the EVAP Purge solenoid open to 100% for at least two seconds.
4. Check the EVAP Sol. Driver display.

Does the display indicate OK while the EVAP sol. is commanded ON?

--

Fault not present. Refer to Diagnostic Aids

Go to Step 9

6

1. Record the fluid life indexes, turn the key to LOCK and wait 30 seconds.
2. Disconnect PCM connector C2.
3. Turn the key ON.
4. Using DMM J 39200 measure the voltage to ground at PCM connector C2 terminal 24.

Is the voltage the same or more than the value specified?

10.0 volts

Go to Step 15

Go to Step 7

7

1. Disconnect the EVAP solenoid connector.
2. Measure the voltage to ground at EVAP solenoid connector terminal A (harness side).

Is the voltage the same or more than the value specified?

10.0 volts

Go to Step 8

Go to Step 11

8

1. Jumper EVAP solenoid connector terminal A to terminal B.
2. Measure the voltage to ground at PCM connector C2 terminal 24.

Is the voltage the same or more than the value specified?

10.0 volts

Go to Step 12

Go to Step 13

9

1. Turn the key to LOCK.
2. Disconnect the EVAP solenoid connector.
3. Turn the key ON.
4. Using DMM J 39200 measure the voltage to ground at EVAP solenoid connector terminal B.

Is the voltage the same or more than the value specified?

0.5 volts

Go to Step 14

Go to Step 12

10 | Repair open or short (blown fuse) in the ignition feed between the fuse, PCM connector C2 terminal 34, the EGR sol., the power steering pressure switch, the MAF sensor and the Transaxle. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | --
11 | Repair the open in the ignition feed between the EVAP solenoid and the splice. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | --
12 | Replace the EVAP solenoid. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | --
13 | Repair open or short to ground in the EVAP Purge Solenoid control circuit between the EVAP solenoid and the PCM. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | --
14 | Repair short to voltage in the EVAP Purge Solenoid control circuit between the EVAP solenoid and the PCM. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | --

15

1. Check terminal contact at the PCM connector C2 terminal 24.
2. Repair terminal contact if needed.

Was terminal contact repaired?

--

Go to Powertrain Control Module Diagnosis for Verify Repair

Go to Step 16

16 | Replace the PCM. Refer to PCM Replacement/Programming . Is the replacement complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | --