P015

DTC PO15:

ECT/Brake Booster Vacuum Sensors And EGR Circuit:

CIRCUIT DESCRIPTION
The Engine Coolant Temperature (ECT) sensor is a thermistor, a sensor whose resistance varies with temperature. The ECT sensor signal is on CKT 410 and sensor ground on CKT 476. As the temperature increases, sensor resistance decreases. High coolant temperature will result in low signal voltage on CKT 410. Code P015 sets because the coolant temperature cannot be less than -29°C when Manifold Air Temperature (MAT) is greater than -23°C.

TEST CONDITIONS
1. Codes P037 and P038 not set.
2. Intake Air Temperature (IAT) sensor value -23°C or greater.

FAILURE CONDITION
Coolant sensor value -29°C or less for 2 seconds.

ACTION TAKEN
1. The Powertrain Control Module (PCM) turns "ON" the Malfunction Indicator Lamp (MIL) (Service Engine Soon).
2. PCM uses the IAT sensor values in place of the engine coolant temperature sensor for the first 4.25 minutes of engine operation, and a value of 90°C afterwards.
3. Transaxle shift adapts are maintained at current levels.

NOTES ON FAULT TREE
1. With the ECT sensor or wiring open circuited, PCM Data PD04 will read -29°C or less.
2. Checking for an open in CKT 410 from PCM to sensor. If PD04 shows 135° - 151°C with the coolant temperature sensor wiring harness terminals jumpered together, then CKTs 410 and 808 are OK.
3. Checking for an open in the sensor ground CKT 808 from sensor pin "A" to the ground splice. If shorting pin "A" to ground causes PD04 to show 135° - 151°C, then there is an open in CKT 808.
4. Checking the PCM's ability to recognize low voltage on terminal "1B5" ECT sensor input. If grounding terminal "1B5" causes PD04 to show 135° - 151°C, then there is an open in CKT 410 from the PCM to the coolant temperature sensor.