For 1990-2009 cars

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Important: Perform the following tests with the engine coolant at ambient temperature. Use a digital multimeter (DMM) at the coolant heater cord flat terminals in order to inspect the resistance of the entire coolant heater circuit. Is the reading higher than the specified value? | 45ohms | Go to Step 2 | Go to Step 5
2 | Inspect the entire coolant heater cord. Is the coolant heater cord frayed, split or cut? | -- | Go to Step 8 | Go to Step 3
3 |

1. Disconnect the engine coolant heater cord from the coolant heater.
2. Inspect the coolant heater cord connector terminals for looseness or damage.

Are either of the coolant heater cord connector terminals loose or damaged?

--

Go to Step 8

Go to Step 4

4 | Use the DMM at the coolant heater terminals in order to inspect the resistance of the coolant heater. Is the reading higher than the specified value? | 43ohms | Go to Step 9 | Go to Step 8
5 | Use the DMM at both of the coolant heater cord flat terminal and at the battery ground (negative) terminals in order to inspect the coolant heater circuit for a short to ground. Does the reading indicate a short to ground? | -- | Go to Step 6 | Go to Step 7
6 |

1. Disconnect the engine coolant heater cord from the engine coolant heater.
2. Use the DMM at the coolant heater cord connector terminals in order to inspect the coolant heater cord for a short to engine ground.

Does the reading indicate a short to engine ground?

--

Go to Step 8

Go to Step 8

7 |

1. Disconnect the engine coolant heater cord from the engine coolant heater.
2. Use the DMM at the coolant heater cord connector terminals in order to inspect the coolant heater cord for an internal short.

The tests indicate that the coolant heater and the coolant heater cord are OK. It is VERY unlikely, that the coolant heater has an internal short. Ensure that the coolant heater is plugged into a good power supply.

Does the reading indicate an internal short.

--

Go to Step 8

Go to Testing for Intermittent Conditions and Poor Connections

8 | Replace the engine coolant heater cord. Refer to Coolant Heater Cord Replacement . Does the customer concern still exist? | -- | Go to Step 1 | System OK
9 | Replace the engine coolant heater. Refer to Coolant Heater Replacement . Does the customer concern still exist? | -- | Go to Step 1 | System OK