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Knock Sensor/Fuel Sensor


Rich

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Ten degrees F this AM in New York. Car is parked outdoors. 1997 Eldorado T purchased new, properly serviced in good condition, 133,000 miles. Got in this AM and had a hard start. Maybe not hard, just an unusually long crank before firing. Battery is three years old, alternator charging at around 14.4 while running. Once it kicked over, ran fine and smooth but the "Service Engine Soon" light came on and stayed on (amber light). After driving for a bit I ran for codes and got the following:

PCM P0325H

PCM B0533H

PCM B1971H

PCM B1983H

MMM B2144H

I looked them up and the first one has something to do with the knock sensor, the second with the fuel sensor. I don't understand the third and fourth, and the fifth one has something to do with the left side mirror position. The car seems to be running fine, nothing I can feel from thr driver seat. But the "Service Engine Soon" light won't go off, even after three driving cycles now. All codes are History codes, not Current, so I wouldn't even be especially concerned were it not for the "Service Engine Soon" light. Before I bring this in to a mechanic, does this look like a costly problem to repair? I wish I could provide more information. Any opinions would be appreciated. Thanks much.

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The first code... P0325, is the one that turned on the Service Engine Soon light.

Since it was so cold and you had a long crank time, the battery "MAY" have dropped to a low enough voltage to cause the various codes to set.

The first thing i would do is clear all the codes and see if any of them come back.

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sometimes it takes more than 3 cycles depending on the code and if it occured again in a different cycle. Also if the condition exists only on a cold start it may need to monitor the next cold starts for reoccurance.

I am also thinking it could have been a voltage drop that caused the codes to set. Does it start good now?

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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I don't think the long crank is fuel pump related. It's definitely the brutal cold after cold soaking outside for the past few days. Subsequent starts today were fine. Started right up. It has been unusually cold here lately, in the teens and single digits by night. What I need to know is how to reset the codes and get rid of the "Service Engine Soon" light to see if the codes and light return.

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turn ignition on

Hold climate control buttons OFF and Passenger Warmer for 3 seconds til all lights flash.

push arrow down until pcm? is displayed

push arrow up

push arrow down til pcm clear codes is displayed,

push arrow up.

Dash should display pcm codes cleared

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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This is turning out to be too easy. I began the day with what I thought was a problem and now it's gone. I just went out to do the reset and upon startup, the "Service Engine Soon" light did not display. It must have reset itself over the past several hours. I drove the car for about twenty minutes without issue. Maybe it's time to start thinking about a new battery. You guys are all terrific. I can't tell you how helpful this site has been over the years, a tremendous resource. The collective knowledge available here is absolutely astounding to me. I've been a member here for ten years now and and grow more confident every time a problem is encountered and then slayed. I only wish you could all share a glass of Chivas with me as I celebrate my Eldorado being back in service (was never out of service really). Again, thanks to all. Jim, your diagnosis hit the nail right on the head. Cheers!!!

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  • 5 months later...

Can anyone help me out I have a 95 seville and it is showing the knock sensor circuitry failure code and I've noticed an unhurt gas smell once in a while anyone know of a site that shows a step by step for changing it I know it's on the back of the engine between the first and 3 piston but not sure how to replace it

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I presume that this is your code:

P132 (E132) Knock Sensor Circuitry Failure

IN OBD II Northstars, the knock sensor is calibrated with the knock sensor module and they are sold as a set. The module snaps into a socket on the PCM. I don't know what the knock sensor setup is on the OBD I Northstars. Someone with OBD I Northstar experience and FSM needs to step in here.

Knock sensors and modules don't go bad often. Before you install new parts, you should check all the connectors and the wiring harness.

The knock sensor is under the intake manifold. It is screwed into the block. The tightening torque is 14 lb-ft, about the same as a spark plug in aluminum heads.

The knock sensor module is under a cover on the PCM on the OBD II Northstars. The 1997 FSM, page 6-763, says to remove the PCM to get access to the cover, which is held on with two screws. The module is held in with a clamp that is released by pinching it. But since the PCM is entirely different in OBD I Northstars, I would defer to someone who has a FSM for OBD I Northstars, preferably the 1995 model year, to tell us how it is done on your model.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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early or late 95. If it's a late 95 the PCM will be located in the LF corner of the engine compartment. The knock module is under a small cover on the PCM case and the knock sensor is under the intake. I replaced 1 or 2 in my lifetime. Early 95, the PCM is behind the glovebox inside the car and the knock sensor is on the back of the block rightside near tranny. If it's a late 95 I would try to replace the knock sensor module in the PCM.

Edited by barczy01
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The "late 1995" configuration is the same as that of the OBD II Northstars. The knock sensor location on the "early 1995" is in a different place but the knock sensor module is still a snap-in with the PCM. I would replace them as a matched, calibrated pair using the car's VIN to make sure that you have the right one.

Of course, I recommend that you check the wiring and connectors before you replace the knock sensor and module.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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