For 1990-2009 cars
Engine Controls Components
Engine Controls Schematics
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The PCM uses the serial data circuit to communicate with various other devices and systems in the vehicle. The PCM ensures that communication remains established by monitoring the serial data circuit for state of health messages from the other devices using the circuit. If the PCM detects a loss of state of health serial data message from the EBCM/EBTCM, DTC P1602 will be set.A Class Il serial data communications system is used on this vehicle to allow various modules to communicate and share information with each other. This allows vehicle wiring to be reduced and the transmission and reception of multiple signals over a single wire. The messages carried on a Class II serial data streams are also prioritized. If two messages attempt to establish communications on the data line at the same time, the message with the higher priority will continue. The message with the lower priority message will wait. If a module cannot respond to the PCM, a DTC is stored.

### Conditions for Running the DTC

• | The ignition is on.

• | System Voltage is greater than 8.2 volts.

### Conditions for Setting the DTC

The PCM is detecting a loss of serial data from the EBCM/EBTCM for longer than 5 seconds.

### Action Taken When the DTC Sets

• | The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.

• | A history DTC is stored.

### Conditions for Clearing the MIL/DTC

• | A history DTC will clear after 40 consecutive warm up cycles have occurred without a malfunction.

• | DTCs can be cleared by using the scan tool.

### Diagnostic Aids

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation.

Any circuitry, that is suspected as causing an intermittent complaint, should be thoroughly checked for the following items:

• | Backed out terminals or improper mating.

• | Broken locks.

• | Improperly formed or damaged terminals.

• | Poor terminal to wiring connections.

• | Physical damage to the wiring harness.

• | Corrosion.

#### DTC P1602 - EBCM/EBTCM Serial Data Circuit

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic System Check performed? | -- | Go to Step 2 | Go to the Powertrain On Board Diagnostic (OBD) System Check
2 | Important: If a loss of DLC data has already been diagnosed using the DLC Diagnosis table, clear this DTC and continue diagnosis with the Powertrain On Board Diagnostic (OBD) System Check . Attempt to select ABS data with the scan tool. Can ABS data be displayed? | -- | Go to Step 3 | Go to Step 4
3 |

1. Turn OFF the ignition switch.
2. Disconnect the PCM and the EBCM / EBTCM.
3. Check the serial data circuit for an open between the EBCM/EBTCM and the PCM.
4. If a problem is found, repair as necessary. Refer to Wiring Repairs .

Was a problem found?

--

Go to Step 6

Go to Diagnostic Aids

4 |

1. Check the serial data circuit for a poor connection at the EBCM/EBTCM.
2. If a problem is found, repair as necessary. Refer to Wiring Repairs .

Was a problem found?

--

Go to Step 6

Go to Step 5

5 |

1. Check the serial data circuit for a poor connection at the PCM.
2. If a problem is found, repair as necessary. Refer to Wiring Repairs .

Was a problem found?

--

Go to Step 6

Go to Diagnostic System Check - ABS

6 |

1. Review and record scan tool Fail Records data.
2. Clear DTCs.
3. Operate the vehicle within Fail Records conditions.
4. Using a scan tool, monitor Specific DTC info for DTC P1602.

Does the scan tool indicate DTC P1602 failed?

--

Go to Step 2

System OK