PCM Message Diagnosis Low Engine Coolant Message
Circuit Description
This test checks for a low engine coolant condition. The pressurized coolant bottle is equipped with a level switch which opens when coolant level is low. The PCM monitors the state of this switch through CKT 1478 and measures the time that the switch is open. If the switch is open for longer than a calculated period of time, the PCM signals the IPC/DIC via the data link to turn on the LOW ENGINE COOLANT message.
The calculated period of time, between 2.1 and 26.3 seconds, before a low coolant condition is recognized is based on vehicle speed and acceleration. The higher vehicle speed and acceleration, the longer the time before a low coolant condition will be recognized. Low coolant level message is displayed on the IPC/DIC for the entire ignition cycle.
Diagnostic Aids
The Engine coolant level switch shares a common sensor/switch ground (CKT 451). An intermittent at any of these connections could possibly cause the Low Engine coolant message to remain ON If coolant level is OK.
If the customer complaint is that the coolant level is low but the message does not display, check the engine coolant level switch for binding or stuck closed.
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
-
Checks if low coolant level is causing the message.
-
Checks for a faulty coolant level switch.
-
Checks CKT 451 for an open.
-
This test checks for a short or open in CKT 1478 or a faulty PCM.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Powertrain OBD System Check | |
2 |
Caution: Do not remove the pressure cap from the high fill reservoir while the engine is at normal operating temperature. An unexpected release of hot engine coolant may result in severe burns.
Does the scan tool display OK? | -- | ||
3 |
Does the scan tool display LOW? | -- | Fault not present. Refer to Diagnostic Aids | |
4 |
Does the scan tool display OK when jumpered and LOW when the jumper is removed? | -- | ||
5 |
Does the scan tool display OK when jumpered and LOW when the jumper is removed? | -- | ||
6 |
Is the resistance measured greater than the specified value? | 5 ohms | ||
7 | Check for a short to ground on CKT 1478. Was a short to ground found and repaired? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | |
8 | Check terminal contact at the Engine coolant level switch. Was a terminal contact problem found and repaired? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | |
9 | Check terminal contact at the PCM connector C2 terminal 56. Was a terminal contact problem found and repaired? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | |
10 | Repair open in CKT 1478. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
11 | Replace the PCM. Refer to PCM Replacement/Programming . Is the replacement complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
12 | Replace the Engine coolant level switch. Is the replacement complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
13 | Repair the open in CKT 451. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
PCM Message Diagnosis Low Engine Oil Level Message
Refer to
Engine Oil Level Sensor/ Generator/ EBTCM/ Shift Select Switch
for wiring view.
Circuit Description
The oil level switch is a magnetic reed float style switch which is closed with oil level full and open when oil level is low. The PCM monitors the oil level switch to determine if the oil level is LOW or OK. When the Test Conditions have been met the PCM will monitor the oil level switch input. If a low oil level is indicated the PCM will send a serial data message to the Driver Information center (DIC). The DIC will then indicate the oil level is low. If the Test Conditions have not been met then the PCM ignores the oil level switch input and oil level OK is indicated to the DIC. The engine coolant temperature Test Condition is required to ensure enough time has passed since the engine was last stopped. The time period/coolant temperature difference is to allow enough time for the engine oil to drain back into the oil pan. The colder the current engine temperature is, the larger the drop in temperature necessary. This is to ensure colder, thicker oil has drained back into the oil pan.
Test Conditions
| • | DTC's P0117, P0118 or P0603 not set. |
| • | Engine speed is 0 RPM. |
| • | The current engine coolant temperature is from 5°C to 20°C less than the temperature stored when the engine was last running. |
Important: The oil level switch is mounted to the oil pan at a level below the full level. Removal of the switch may drain several quarts of oil.
Test Description
-
The Powertrain OBD System Check must be performed before proceeding with this diagnosis. Go to any DTC's that are set first.
-
With the engine speed at or above 2300 RPM the engine oil switch should indicate LOW oil level. The engine oil is scavenged to a level that is below the switch during higher engine speed and also during some lateral vehicle movement conditions.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Powertrain OBD System Check | |
2 |
Fill or drain the engine oil if required. Does the display indicate the oil level is OK? | -- | ||
3 |
Does the engine oil level display indicate LOW while engine speed is at the specified value? | 2300 RPM | Fault not present. Refer to Diagnostic Aids | |
4 |
Does the engine oil level display indicate the oil level is OK? | -- | ||
5 | Place the jumper between terminal A and a known good engine ground. Does the display indicate the engine oil is OK ? | -- | ||
6 |
Is the resistance the same or less than the value specified? | 5 ohms | ||
7 |
Does the engine oil level display indicate the oil level is LOW? | -- | ||
8 |
Is the resistance the same or more than the value specified? | 10K ohms | ||
9 | Repair the open in the engine oil level input circuit. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
10 | Repair the open in the engine oil level switch ground circuit. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
11 | Repair the short to ground in the engine oil level switch input circuit. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
12 |
Was the terminal contact repaired? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | |
13 | Replace the engine oil level switch. Is the replacement complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
14 |
Was terminal contact repaired? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | |
15 | Replace the Powertrain Control Module. Refer to PCM Replacement/Programming . Is the replacement complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
