P1250

Diagnostic Chart:

Wiring Diagram:

Circuit Description

The Early Fuel Evaporation (EFE) heater provides a source of rapid heat to the air/fuel mixture during cold start conditions. Rapid heating provides quick fuel evaporation, a more uniform fuel distribution and also reduces the length of time the engine is in Open Loop, reducing the exhaust emission levels. When the Powertrain Control Module (PCM) determines that the engine coolant temperature is below operating temperature and the engine speed is above idle, it will energize the Positive temperature coefficient (PTC) heater relay (EFE heater relay) coil. Voltage will then be applied to the EFE heater through the PTC (EFE) heater relay contacts. When the engine reaches operating temperature, or the engine speed is reduced to idle, the PCM will de-energize the EFE system.

Conditions for Running the DTC

^ Intake air temperature between -10°C (14°F) and 50°C (122°F).

^ Barometric pressure greater than 75 kPa.

^ Fuel tank level is greater than 25%.

Conditions for Setting the DTC

^ Resistor voltage less than 2.5 volts with the EFE heater off.

^ Resistor voltage greater than or equal to 0.3 volts with the EFE heater on.

^ Condition present for 5 seconds.

Action Taken When the DTC Sets

^ The Malfunction Indicator Lamp (MIL) will illuminate after two consecutive ignition cycles in which the diagnostic runs with the fault active.

^ The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame buffer.

Conditions for Clearing the MIL/DTC

^ The MIL will turn OFF after three consecutively passing cycles without a fault present.

^ A History DTC will clear after 40 consecutive warm-up cycles without a fault.

^ DTCs can be cleared by using a scan tool or by disconnecting the PCM battery feed.

Diagnostic Aids

Check for a poor connection at the PCM. Inspect the harness connectors for backed out terminal, improper mating, broken locks, improperly formed or damaged terminals, and a poor terminal to wire connection.

Check for a damaged wiring harness. Inspect the wiring harness for damage and repair as necessary.

If a DTC P1250 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicles operating conditions when the DTC was first set.

If any wiring repairs need to be made, Refer to Repair Procedures in Electrical Diagrams.

Test Description

The numbers below refer to the step numbers in the Diagnostic Table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. Determine if the fault is present.

5. Manually turns ON PTC heater relay to check the battery feed circuit and for proper operation of the PTC heater relay.

13. Before replacing the EFE heater perform the following check: With the ignition OFF disconnect the PTC heater relay and the PCM connectors. With a Digital Multimeter measure the resistance from the EFE ON Signal circuit to ground (harness side). Resistance should be 0.5 to 3.0 ohms at 20° (68°F), if not check for a open or short in the EFE ON Signal circuit to the PCM, repair as necessary and retest.