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.
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Checks if low coolant level is causing the message.
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Checks for a faulty coolant level switch.
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Checks CKT 451 for an open.
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This test checks for a short or open in CKT 1478 or a faulty PCM.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (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 Powertrain Control Module 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 | -- |
