REPLACING PCM

1994 Buick Roadmaster

Tiny

stamphead

April, 6, 2010 AT 10:22 PM

Engine Cooling problem
1994 Buick Roadmaster V8 Two Wheel Drive Automatic 120k miles

Primary fan does not come on, but works when plugged in to secondary side. Secondary fan comes on when a/c is on, but car still runs hot in warm weather. Thermostat replaced last year. Relays checked out OK. Am told I need to replace the pcm.
Is this the next logical step and, if so, where on the vehicle is it located?

1 Answer

Tiny

freemba

April, 19, 2010 AT 6:07 PM

Before replacing the PCM, check the temperature sensor (located on the thermostat housing--at the end of the top radiator hose) it usually has two wires running to it. At operational temp. The sensor sends a signal to the pcm to turn on the fan. If the pcm doesn't get this signal it will not turn on the fan.

**Don't confuse the temp sensor with the temp sending unit. The sending unit is usually locates on the drivers' side cylinder head between the first two spark plugs.

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