If you disconnect the knock sensor but set no codes, does the ECM go into limp home mode anyway? Or does the ECM have to set a code first, then go into LHM?

Just wondering cuz mine is disconnected but I've read that it's not good to do that because the ECM will go into LHM. But my ECM hasn't set any codes, and I haven't done the resistor trick to the knock sensor.

Thanks for the help.

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1989 IROC-Z, ZZ3 shortblock with some bolt-ons.
13.20 @ 108.69, 2.2 60' on "Road Hugger" radials and dead Auburn posi.

 

What's the Resistor trick?

 

A 3.9K resistors that the knock sensor wire is grounded trough.

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92 Z28 L98 350
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Ported and polished heads, ported stock TPI base, ported plenum, Comp Cams XR270HR-10 cam (lift .495/.502 duration 218/224 lobe separation 110), Edelbrock TES headers, LT4 valve springs, Crane AFPR, Flowmaster catback with LT1 style tips, MSD coil & wires...

"Take that auto, drop it in first, hold the brakes, stomp the gas and grin from ear to ear! :-)

 

When your engine first starts, the ECM purposely tests the Knock Sensor to test its limits. I have seen this on my Diacom. If the ECM does not see a Knock detected, it may cause it to set the SES light and/or go into Limp mode. A resistor MAY not do the trick for you, as the ECM may not see a Knock detected, which it is expecting.

 

The resistor trick works great. I have it on my car wired into a SPDT switch. One direction on the switch is wired to the KS and the other direction is wired to the 3.9K Ohm resistor which is then wired to ground.

Tim

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TRAXION's 1990 IROC-Z
Best Time = 12.587 @ 107.97mph (1.710 60ftr) on the long runner setup.
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels. Stock Wheels. No Weight Reduction.
Gunning for NA 11's with the MiniRam II and Hooker LT Headers.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org