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Power-train Control Module (PCM) location

Tiny
STEVE90819
  • MEMBER
  • 1998 CHEVROLET LUMINA
  • 3.1L
  • V6
  • 2WD
  • AUTOMATIC
  • 216,000 MILES
Where is the Power-train Control Module (PCM) located?

I don't see any modules forward of the strut tower on the passenger side.

All I see on that side is the coolant reservoir and a black plastic box containing fuses and relays.
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Monday, August 19th, 2019 AT 10:39 AM

5 Replies

Tiny
BMDOUBLE
  • MECHANIC
  • 1,139 POSTS
It is in that plastic box at the right front strut tower.
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Monday, August 19th, 2019 AT 12:59 PM
Tiny
STEVE90819
  • MEMBER
  • 3 POSTS
Is that the one hiding below the box that has the fuses, and the relays for Fan2 and Fan1?

Could you please post instructions for how to gain access to it?

I'm asking because: The radiator fans stopped working, so the engine slowly overheats when stopped at a traffic light or caught slow moving traffic.

I tested the fan motors, the fuses, and the relays. They're all good.

I tested all the wiring against the cooling fan circuit schematic, and they're all good.

Except I haven't yet been able to test the 2 wires (dark blue and dark green) going to the PCM (pins 5 and 6) from the 3 fan relays.

The PCM uses those wires to turn the fan relays on by grounding the wires, which allows current to flow through the relay coils, turning the relay switches on.

I'm hoping it's just a bad connection, and not a failed circuit in the PCM.

Does the PCM on this engine have a known issue of failing in this manner?
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Monday, August 19th, 2019 AT 1:34 PM
Tiny
BMDOUBLE
  • MECHANIC
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My apologies, it's at the right strut tower inside the air filter housing as the illustration shows. You just have to remove the top of the air filter housing to access the connector and pcm. As far as a common failure, there are many drivers that fail in these cars and the fan can be one of them.
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Monday, August 19th, 2019 AT 3:51 PM
Tiny
STEVE90819
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  • 3 POSTS
That's not the air filter housing.

The air filter housing is on the driver's side of the engine.

Can someone please post a link to detailed step-by-step instructions for gaining access to the PCM, including how to remove the PCM connector to gain testing access to the pins/sockets. Thank you
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Monday, August 19th, 2019 AT 4:15 PM
Tiny
BMDOUBLE
  • MECHANIC
  • 1,139 POSTS
Left side, I'm a little dyslexic sorry.
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Tuesday, August 20th, 2019 AT 7:01 AM

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