Circuit Description
The serial data communications circuit (CKT 800) transmits messages from one electronic control module to another when interface between systems is necessary. The ABS VI/TCS systems depend on information to and from the PCM for proper operation.
Conditions for Setting the DTC
DTC C1275 will set if either of the following conditions occurs:
| • | The vehicle speed is greater than 5 km/h (3 mph) and a malfunction exists on the serial data circuit. |
| • | The PCM has not broadcasted a serial message for at least 10 seconds. |
Action Taken When the DTC Sets
| • | A malfunction DTC stores. |
| • | The TCS disables. |
| • | The amber TCS warning indicator turns on. |
| • | The ABS remains functional. |
| • | No action towards the Electronic Brake Control Relay and ABS warning indicator is taken. |
Conditions for Clearing the DTC
| • | The condition responsible for setting the DTC no longer exists and the Scan Tool Clear DTC function is used. |
| • | 100 drive cycles pass with no DTC detected. |
Diagnostic Aids
When DTC 1275 is current (malfunction in CKT 800), no communication can be established with the scan tool. When the malfunction is removed, DTC C1275 will be stored in system memory. Use the enhanced diagnostic function of the Scan Tool to measure the frequency of the malfunction. Refer to the Scan Tool manual or Scan Tool Diagnostics located in this section for the procedure.
Thoroughly inspect any circuitry that may cause the intermittent complaint for the following conditions:
| • | Rubbed-through wire insulation |
| • | A broken wire inside the insulation |
| • | Backed out terminals |
| • | Improper mating |
| • | Broken locks |
| • | Improperly formed or damaged terminals |
| • | Poor terminal-to-wiring connections |
| • | Physical damage to the wiring harness |
Important: Zero the J 39200 test leads before making any resistance measurements.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Diagnostic System Check performed? | -- | Go to Step 2 | Go to Diagnostic System Check | ||||||
2 | Use the Scan Tool in order to establish communication with the same system on a different vehicle. Can communication be established on a different vehicle? | -- | Go to Step 3 | Go to Step 19 | ||||||
3 |
Is there poor terminal contact, terminal corrosion, or terminal damage? | -- | Go to Step 13 | Go to Step 4 | ||||||
4 |
Can communication be established with the other modules that are connected to the serial data line? | -- | Go to Step 11 | Go to Step 5 | ||||||
5 |
Is continuity present to ground during this test? | -- | Go to Step 14 | Go to Step 6 | ||||||
6 |
Is the voltage equal to the specified value? | 0V | Go to Step 7 | Go to Step 15 | ||||||
7 |
Can communication be established with the inflatable restraint diagnostic energy reserve module (SDM)? | -- | Go to Step 8 | Go to SIR System Check | ||||||
8 |
Can communication be established with the driver information center (DIC)? | -- | Go to Step 9 | Go to DIC System Check | ||||||
9 |
Can communication be established with the PCM? | -- | Go to Step 10 | Go to OBD System Check | ||||||
10 |
Can communication be established with the EBCM/EBTCM? | -- | Go to Step 18 | Go to Step 17 | ||||||
11 |
Is there poor terminal contact, terminal corrosion, or terminal damage? | -- | Go to Step 13 | Go to Step 12 | ||||||
12 | Use the J 39200 in order to measure the resistance between the data link connector (DLC) terminal 9 and the 24-way EBCM/EBTCM connector C1 terminal A1. Is the resistance within the specified range? | 0-2ohms | Go to Step 17 | Go to Step 16 | ||||||
13 | Replace all the terminals or connectors that exhibit the following conditions:
Is the repair complete? | -- | Go to Diagnostic System Check | -- | ||||||
14 | Repair the short to ground in CKT 800. Is the repair complete? | -- | Go to Diagnostic System Check | -- | ||||||
15 | Repair the short to voltage in CKT 800. Is the repair complete? | -- | Go to Diagnostic System Check | -- | ||||||
16 | Repair the open in CKT 800 between the data link connector (DLC) terminal 9 and the 24-way EBCM/EBTCM connector C1 terminal A1. Is the repair complete? | -- | Go to Diagnostic System Check | -- | ||||||
17 | Replace the EBCM/EBTCM. Refer to Electronic Brake and Traction Control Module Replacement . Is the repair complete? | -- | Go to Diagnostic System Check | -- | ||||||
18 | The malfunction is intermittent or not present at this time. Is a concern still present? | -- | Go to Diagnostic Aids | Go to Diagnostic System Check | ||||||
19 | The Scan Tool may be malfunctioning. Is the scan tool unable to communicate? | -- | Go to the Scan Tool manual. | Go to Diagnostic System Check |
