For 1990-2009 cars

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Data Link Communications System Check performed? | -- | Go to Step 2 | Go to Data Link Communications System Check
2 | Attempt to establish communication with the other modules connected to the circuit.

• | Electronic Brake Traction Control Module (EBTCM)

• | Power Steering Control Module (PSCM)

• | SIR Module

Does the scan tool communicate with the other modules?

--

Go to Step 3

Go to Step 4

3 |

1. Disconnect the heater and A/C control connector C1.
2. Measure the resistance between connector C1 terminal 17 and the data link connector (DLC) terminal 12.

Does the resistance measure less than the specified value?

5 ohms

Go to Step 5

Go to Step 6

4 |

1. Disconnect the EBTCM connector.
2. Attempt to communicate with the other modules.

Does the scan tool communicate with the other modules?

--

Go to Step 7

Go to Step 8

5 | Inspect for poor connections at connector C1 terminal 17. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems. Did you find and correct the poor connection condition? | -- | Go to Step 9 | Go to Step 10
6 | Locate and repair an open in the heater and A/C control serial data circuit. Is the repair complete? | -- | Go to Step 9 | --
7 | Replace the EBTCM. Is the replacement complete? | -- | Go to Step 9 | --
8 |

1. Reconnect the EBTCM.
2. Disconnect connector C1 from the heater and A/C control.
3. Attempt to communicate with the other modules.

Does the scan tool communicate with the other modules?

--

Go to Step 12

Go to Step 13

9 | Attempt to establish communications with the heater and A/C control. Does the scan tool communicate with the heater and A/C control? | -- | System OK | Go to Step 2
10 |

1. Inspect the HZD fuse for an open.
2. Inspect and test the heater and A/C control battery feed circuit at connector C1 terminal 22 for proper voltage (11-13 V).
3. Inspect and test the heater and A/C control ground circuit at connector C1 terminal 21.
4. Make necessary repairs.

Did you find and correct any conditions?

--

Go to Step 9

Go to Step 12

11 | Replace the PSCM. Is the replacement complete? | -- | Go to Step 9 | --
12 | Replace the heater and A/C control. Is the replacement complete? | -- | Go to Step 9 | --
13 |

1. Reconnect the heater and A/C control.
2. Disconnect the PSCM connector.
3. Attempt to communicate with the other modules.

Does the scan tool communicate with the other modules?

--

Go to Step 11

Go to Step 14

14 |

1. Reconnect the PSCM.
2. Disconnect the SIR module connector.
3. Attempt to communicate with the other modules.

Does the scan tool communicate with the other modules?

--

Go to Step 15

Go to Step 16

15 | Replace the SIR module. Is the replacement complete? | -- | Go to Step 9 | --
16 | Test the serial data circuit, of the DLC, for a short to ground between terminal 12 and each module.

• | EBTCM connector terminal 11

• | Heater and A/C Control connector C1 terminal 17

• | SIR Module terminal 12

• | PSCM connector terminal 1

Did you find a short to ground in the serial data circuit?

--

Go to Step 17

Go to Step 18

17 | Locate and repair the short to ground in the serial data circuit. Is the repair complete? | -- | Go to Step 9 | --
18 | Test the serial data circuit, of the DLC, for a short to voltage between terminal 12 and each module.

• | EBTCM connector terminal 11

• | Heater and A/C Control connector C1 terminal 17

• | SIR Module terminal 12

• | PSCM connector terminal 1

Did you find a short to voltage in the serial data circuit?

--

Go to Step 19

Go to Step 2

19 | Locate and repair the short to voltage in the serial data circuit. Is the repair complete? | -- | Go to Step 9 | --