: Random CE Light When Cruising?



DopeStar 156
08-16-09, 11:57 PM
Drove to the shore this weekend with my Fleetwood, problem free with the exception of the Check Engine light coming on at random times while cruising for a minute then going out. I pilled the codes when I got home and got these....

-Code 31: Canister Purge Solenoid Circuit
-Code 45: Rich O2 Signal

I'm assuming that 31 is causing the rich O2 signal since it is part of the emissions system. Does anyone have any thoughts to what's happening here and how I can look into fixing this?

sven914
08-17-09, 01:38 AM
To test the canister purge solenoid you are going to need a 12volt test lamp and DVOM.

The procedure for diagnosing and repairing code 31 is as follows:

1 Disconnect the canister purge solenoid (it is on the front passenger side of the engine and should be mounted to the valve cover). Connect the test from terminal A to terminal B on the wiring harness (A has the pnk/blk wire and B has a grn/yel wire). Turn the ignition to the run position, but DO NOT start the engine. Observe the test light. If the light is on, then there is a short to ground at CKT 428 (the wire that goes from terminal B to the ECM); if 428 is not shorted to ground, then the ECM is bad and needs to be replaced. If the light is off, continue to step 2.

2. Connect the test light from terminal A to chassis ground and observe the test light. If the light is off, then there is a short to ground at CKT 39 (the wire that goes from terminal A to the ignition). If the light is on, then continue to step 3.

3. Connect the the test lamp from terminal A to Terminal B. Put the car into diagnostic mode using the ALDL (by jumping the last two terminals on the top row together) If the test light is off, then check for broken wire at CKT 428, of a fault connection to the ECM terminal 17. If the light is on, then continue to step 4.

4. Using a DVOM, measure the resistance of the canister purge solenoid (terminals A&B of the solenoid, not the harness). If the resistance reading is not at least 20 ohms, then replace the canister purge solenoid. If the reading is at least 20 ohms, then continue to step 5.

Check for faulty connections at the canister purge solenoid. If one is found repair it. If there are no faulty connections then "NO FAULT FOUND."

Also check the vacuum line to and from the canister. And yes if the canister purge isn't working properly, it will cause the O2 to read rich. For all of your diagnostic needs, I recommend an OEM factory service manual (http://shop.ebay.com/?_from=R40&_trksid=p3907.m38.l1313&_nkw=1989+Cadillac+Brougham++service+manual+&_sacat=See-All-Categories).

DopeStar 156
08-17-09, 09:10 AM
I know, I have one but I thought there might be an easier method to figure this out than the test light thing and all that.... I figure someone with this problem could come up and say "oh yeah I had this, do this and it'll prolly fix it......"

77CDV
08-18-09, 02:18 AM
To test the canister purge solenoid you are going to need a 12volt test lamp and DVOM.

The procedure for diagnosing and repairing code 31 is as follows:

1 Disconnect the canister purge solenoid (it is on the front passenger side of the engine and should be mounted to the valve cover). Connect the test from terminal A to terminal B on the wiring harness (A has the pnk/blk wire and B has a grn/yel wire). Turn the ignition to the run position, but DO NOT start the engine. Observe the test light. If the light is on, then there is a short to ground at CKT 428 (the wire that goes from terminal B to the ECM); if 428 is not shorted to ground, then the ECM is bad and needs to be replaced. If the light is off, continue to step 2.

2. Connect the test light from terminal A to chassis ground and observe the test light. If the light is off, then there is a short to ground at CKT 39 (the wire that goes from terminal A to the ignition). If the light is on, then continue to step 3.

3. Connect the the test lamp from terminal A to Terminal B. Put the car into diagnostic mode using the ALDL (by jumping the last two terminals on the top row together) If the test light is off, then check for broken wire at CKT 428, of a fault connection to the ECM terminal 17. If the light is on, then continue to step 4.

4. Using a DVOM, measure the resistance of the canister purge solenoid (terminals A&B of the solenoid, not the harness). If the resistance reading is not at least 20 ohms, then replace the canister purge solenoid. If the reading is at least 20 ohms, then continue to step 5.

Check for faulty connections at the canister purge solenoid. If one is found repair it. If there are no faulty connections then "NO FAULT FOUND."

Also check the vacuum line to and from the canister. And yes if the canister purge isn't working properly, it will cause the O2 to read rich. For all of your diagnostic needs, I recommend an OEM factory service manual (http://shop.ebay.com/?_from=R40&_trksid=p3907.m38.l1313&_nkw=1989+Cadillac+Brougham++service+manual+&_sacat=See-All-Categories).

So what's step 5? And what does one do if "NO FAULT FOUND"?:hmm:

sven914
08-18-09, 03:28 AM
I forgot to number it. Step 5 is "check for faulty connections." and "no fault found" means just that; the diagnostic process turned up no problem with the system being checked. That is when a good tech starts thinging outside the box, because there is defiantly a problem with the car, but not were the computer says it is. So you have to start thinking about the circumstances where the computer will think one electronic device is bad when it was another one that crapped out.

77CDV
08-20-09, 01:22 AM
Oh, goody, I can think of nothing better than playing "I've got a secret" with the car's computer. No wonder I prefer the older, non-computerized cars.