Code 27 QDM 3 = New ECM for 92 LT1 ?
Thread Starter
Drifting
Joined: Sep 2003
Posts: 1,585
Likes: 4
From: Agoura Hills CA
Code 27 QDM 3 = New ECM for 92 LT1 ?
92 LT1 6spd, 45k
Checked the codes in trying to trouble shoot my intermittent high idle (will hang at 2,000 rpm, the sometimes slowly step down to 600 rpm) came up with - 27 QDM 3.
I have cleared the code numerous times but keeps coming back, car has run fine while the code has come back. My Service Manual shows a QDM 3 should be a code 28 ??
So far I have disconnected my current ECM, Inspected all pins and wires, removed PROM, used light air gun to clean inside ECM, reassembled, still throwing a 27 QDM 3.
Car runs great other than the intermittent hanging idle.
Thoughts / Suggestions ?
Ed B.
Checked the codes in trying to trouble shoot my intermittent high idle (will hang at 2,000 rpm, the sometimes slowly step down to 600 rpm) came up with - 27 QDM 3.
I have cleared the code numerous times but keeps coming back, car has run fine while the code has come back. My Service Manual shows a QDM 3 should be a code 28 ??
So far I have disconnected my current ECM, Inspected all pins and wires, removed PROM, used light air gun to clean inside ECM, reassembled, still throwing a 27 QDM 3.
Car runs great other than the intermittent hanging idle.
Thoughts / Suggestions ?
Ed B.
Burning Brakes
Joined: May 1999
Posts: 760
Likes: 1
From: Greenwich, CT
From a web search for ECM codes -
27 Quad Driver Module Number 2:
Potential ECM or on a manual transmission car, potential upshift relay problem. Check
relay, replace if less than 18 Ohms using a digital Ohm Meter.
28 Quad Driver Module Number 3:
Air conditioning Clutch relay and/or cooling fan relays. Check with digital Ohm meter,
replace if less than 18 Ohms. If relays OK, potential ECM failure.
If it were mine I'd probably replace the relays (and fuses) with fresh ones anyway - if that
doesn't cure the situation, you've possibly blown out some of the power transistors (quad
driver) on the ECM mainboard and will need a new ECM ASAP. I say ASAP so that you don't
fry some other components by continuing to drive around with faulty electricals... or set
fire to something expensive.
I'd further check the AC clutch and cooling fans (and maybe the CAGS bypass?) to make sure
they're operating properly, on the off-chance a problem there precipitated the whole event.
27 Quad Driver Module Number 2:
Potential ECM or on a manual transmission car, potential upshift relay problem. Check
relay, replace if less than 18 Ohms using a digital Ohm Meter.
28 Quad Driver Module Number 3:
Air conditioning Clutch relay and/or cooling fan relays. Check with digital Ohm meter,
replace if less than 18 Ohms. If relays OK, potential ECM failure.
If it were mine I'd probably replace the relays (and fuses) with fresh ones anyway - if that
doesn't cure the situation, you've possibly blown out some of the power transistors (quad
driver) on the ECM mainboard and will need a new ECM ASAP. I say ASAP so that you don't
fry some other components by continuing to drive around with faulty electricals... or set
fire to something expensive.
I'd further check the AC clutch and cooling fans (and maybe the CAGS bypass?) to make sure
they're operating properly, on the off-chance a problem there precipitated the whole event.
