Check Engine Light

Tiny
MMPRINCE4000
  • MECHANIC
  • 8,548 POSTS
I would remove the ingition module and have it tested, this is free at most autoparts stores.
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Tuesday, June 23rd, 2020 AT 5:23 PM (Merged)
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
First thing you need to do is read the codes, look under the dash and find the ALDL, this is a small diagnostic connector then do this: PROCEDURES FOR READING GM FLASH CODES
1. Turn the ignition switch ON but do not start the engine.
2. The "CHECK ENGINE" light come on indicating the bulb is working. If the light fails to come on, the bulb may be burned
out or there may be a problem in the Check Engine light circuit.
3. Locate the diagnostic connector for the computer. It is usually located under the instrument panel near the steering
column. Insert a jumper between the "TEST" and "GROUND" terminals.
CAUTION: Refer to a shop manual for the proper terminal locations. Jumping the wrong terminals may cause damage to the
computer system!
4. The Check Engine should now flash. The first code should be a code 12 (Flash, Pause, Flash Flash). Code 12 will repeat
two times.
If any other trouble codes are in the computer's memory, they will be displayed in numerical order starting with the lowest
number, and repeat three times. The codes will continue to repeat as long as the test terminal remains grounded.
NOTE: BE SURE TO WRITE DOWN ANY CODES THAT ARE PRESENT
NOTE: GM may use the same code number for different faults on different models of vehicles. That's why some code
numbers list more than one possible cause.
5. To exit diagnostic mode, turn ignition switch off and remove the jumper.
HOW TO CLEAR TROUBLE CODES
Trouble codes on most older vehicles can be cleared by removing battery voltage from the computer for at least 10 seconds.
Make sure the ignition switch is OFF, then remove the computer fuse from the fuse panel. Disconnecting the battery will also
work, but doing so will also cause the loss of stored information and presets in other electronic accessories such as the
radio, climate control system, memory seats, etc. Disconnecting the battery can also cause the computer to forget long term
fuel calibration adjustments, and may affect the operation of an electronic transmission until the computer can "relearn" the
shift points.
The preferred method of clearing trouble codes is to use a scan tool.
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Tuesday, June 23rd, 2020 AT 5:23 PM (Merged)
Tiny
ROBERTC
  • MEMBER
  • 2 POSTS
  • 1992 OLDSMOBILE 88
  • 140,000 MILES
Oldsmobile 88 Royal 1992 intermittent check engine light (code 41). Engine performance never changes. No set time or condition when it occurs or goes out or comes back on or goes out again. Checked Cam Sensor connertor and wiring to ECM. Replacer ECM with a spare ECM. No change.
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Tuesday, June 23rd, 2020 AT 5:23 PM (Merged)
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Intermittent issues can be a pain to track. You have to test when the problem is ongoing. Because the crank and cam sensors share ref voltage and ground, I'd have to check the crank sensor also.

If you live in a state that doesn't do vehicle inspections and no driveability issues? My state hasn't done vehicle inspections in years.
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Tuesday, June 23rd, 2020 AT 5:23 PM (Merged)
Tiny
ROBERTC
  • MEMBER
  • 2 POSTS
JDL TY for your help

UP-DATE 28 Sept 2011
ECM and Crank Sensor were replaced Mar 2001.
Replaced Cam Sensor and Check Engine Light is constant now. Removed Cam Sensor and rotated engine to inspect Magnet. No Magnet, only some what looks like some metal shavings and plastic holder. Guess there was enough magnet/shavings there to give intermittent reading.

While I have this all torn apart I am putting in new Timing Gears, rebuilding the Oil Pump and replace the Camshaft Interrupter. Now I know why a shop wanted $900 just to replace the Camshaft Interrupter.

It is recommended that I epoxy the Camshaft Interrupter to the cam gear.
Is this a good idea?
The magnet in the Camshaft Interrupter appears to be incased in plastic.
What could have caused the top of the Camshaft Interrupter to have worn away?
Should I place a drop of epoxy on the magnet to plastic also?

Will rotate engine after replacing timing gears to align Camshaft Interrupter with Cam Sensor opening in timing chain cover. There are no adjustments that I can find for the Camshaft Interrupter or Cam Sensor. Is there anything special I should look for before putting this all back together?
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Tuesday, June 23rd, 2020 AT 5:23 PM (Merged)
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Looks to me like you got it all covered. Using the epoxy is fine, I've never used it on the magnet, itself?
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Tuesday, June 23rd, 2020 AT 5:23 PM (Merged)

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