PCM turns on SERVICE ENGINE SOON light. PCM uses 104°F (40°C) for a MAT value when coolant temperature is greater than 104°F (40°C). PCM substitutes coolant temperature for MAT temperature when coolant temperature is less than 104°F (40°C).

NOTE: Test numbers refer to numbers on diagnostic chart.

If sensor is open, PCM parameter ED05 should indicate -35°C or less. If ED05 does not indicate -35° or less, sensor signal is not open at this time. See NOTE ON INTERMITTENTS.
Checks PCM and sensor circuitry from PCM to sensor connector. If PCM parameter ED05 indicates 148-151°C with connector terminal "A" shorted to terminal "B", sensor circuits and PCM are okay.
Checks for open sensor ground.
Checks PCM ability to recognize short to ground on MAT input.
Fault is most likely at PCM connector or PCM. Check for damaged PCM terminals or poor connection before replacing PCM.
MAT sensor can be damaged by backfire in intake or by excessive intake heat due to valve train faults. If vehicle has had multiple MAT sensor replacements, check for signs of backfire or high intake manifold air temperature due to improper valve train operation.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Pcm Code E038, Open Mat Sensor Circuit: Action

Use the Manual With the Right Hardware

When to See a Mechanic

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