the problem i'am having is that my (SES) light comes on and it says it is the o2 sensor is bad , well i put new one in and the same problem again code (13) i disconnected the battery after the swap. when i check the live data with my scan tool the ecm is not going into closed loop and the o2 reads 448mv thats at full temp with a 180 temp stat , everthing is stock on my car , any ideas as to what is setting off this code! some times it will go into closed loop and i can read the the data from the o2 and it reads any where from 100mv to around 900mv the car runs fine just a concern about this open loop thing!

 

Code 13 will set if you have an open. It could be any of the following: O2 sensor, wiring or the ECM itself. I believe you may rule out a O2 sensor since you've already replaced that. Here is some more info to help you find the problem:

CODE 13 - OXYGEN SENSOR CIRCUIT (OPEN CIRCUIT)

Circuit Description:
The Electronic Control Module (ECM) supplies a voltage of about .45 volt between terminals "D2" and "D6". (If measured with a 10 megohm digital voltmeter, this may read as low as .32 volt.) The 02 sensor varies the voltage within a range of about 1 volt if the exhaust is rich, down through about .10 volt if exhaust is lean. The sensor is like an open circuit and produces no voltage when it is below 360 degrees C (600 degrees F). An open sensor circuit or cold sensor causes open loop operation.



Test Description: Numbers below refer to circled numbers on the diagnostic chart.

Code 13 will set if: Engine at normal operating temperature (above 70 degrees C) At least 2 minutes engine time after start O2 signal voltage steady between .35 and .55 volt Throttle position sensor signal above 5% (about .3 volt above closed throttle voltage) All conditions must be met for about 60 seconds If the conditions for a Code 13 exist the system will not go "Closed Loop".
This will determine if the sensor is at fault or the wiring or ECM is the cause of the Code 13.
In doing this test use only a high impedence digital volt ohmmeter. This test checks the continuity of CKTs 412 and 413. If CKT 413 is open, the ECM voltage on CKT 412 will be over .6 volt (600 mV).

Diagnostic Aids:

Normal "Scan" voltage varies between 100 mV to 999 mV (.1 and 1.0 volt) while in "Closed Loop". Code 13 sets in one minute if voltage remains between .35 and .55 volt, but the system will go "Open Loop" in about 15 seconds. Refer to "Intermittents" in DIAGNOSIS BY SYMPTOM - NO TROUBLE CODE STORED.

Also Check-Out this thread I have posted a pic of the O2 Sensor Circuit in there: https://www.thirdgen.org/techbb2/sho...hreadid=247579

 

This may not apply to you but a couple of weeks ago i took my coil off.When i went to put it back on i forgot to put the ground wire that goes underneath the coil back on.I fired it up and i also got a code 13.After looking around i saw the ground wire hanging and reattached it.That took care of it.Good luck and hope this may be of some help.

 

Idid some more testing , what i did was load the car up with A/C on and got the temp up to 191 and it went into closed loop and stayed there, i think i might put the 195 stat back in to see if that helps , i noticed the gas milage has gone down and it smells a little rich at idle, this is due to open loop operation , when does the ecm go into closed loop, providing everything is operating properly at what temp! keep in mind this is a stock prom and motor! my (TPS) is 5.38 volts . my fans are always enabled thats another issue, so the motor will only get about 7to8 degrs f over the 180 stat

 

another question i for got to ask is , if i do an engine biuld up such as a 355 with all mods heads, cam etc will an after market chip help put this thing into closed loop sooner or is it up to the o2 the switch into clsd loop when it reaches it's desired temp!

 

Bear with me on this. From reading your post I take it that your kind of new to Computer Controlled Engines. The Ecm/Pcm is just like your brain, it has both inputs and outputs. If a book falls on your big toe, your going to yell and reach down and grab-it. In the same way, the sensors on the engine feed information to it in the form of electricial signals. It can be an on/off switch like a hall-effects or a resistor changing the constaint voltage as is in the TPS. The Ecm/Pcm processes these signals and inturn sends instructions to the injectors, fans and other componets of the EFI.

When an engine is first started of a morning, its running in whats know as open loop mode. This mode is designed to get the engine started and running to where it can then go into closed loop mode. While an engine is running in Open Loop, it will also run rich this is the way they design the programming. When the engine meets certain conditions the Ecm/Pcm will then go into what is known as Closed Loop. If for some reason the Ecm can not go into closed loop the engine will stay in open loop. There is also a mode known as Limp Mode. If the EFI system developes a problem the Ecm will drop out of Closed loop and go into Limp Mode. This mode is designed to get you home and to a shop where you can then get it fixed. Both Open Loop and Limp Mode run fuel enriched.

Gathering from what you've stated I'd say your car is running in open loop. 350 TPI described how he left a ground wire off and caused a code 13 to pop up. You've already replaced your O2 sensor which didn't seem to make a difference. And since your posting suggest that you have and know how to use a multimeter. I would check your wiring and grounds to ensure no problems. Also when checkingyour wiring don't forget to do a "Wiggle Test." Sometimes a wire can have a break in it causing a intermitte problem that shows up while the engine is running and viberating . Using the flow chart which I posted will help you identify your problem if used corretly.

As far as your second question, you first need to correct the first problem of a code 13 before doing an engine build-up. Otherwise you'll end up with a bigger mess on your hands and you'll still have a code 13 to deal with.

Here is a good site with a lot of info on the TPI Fuel system http://www.customefis.com/GMEFI.html

Good Luck
Bill

 

Seems when I made a change earlier the flow chart dropped off.

 

Here is the intermittent part:

Intermittent malfunctions may occur which may or may not cause the "Check Engine" or "Service Engine Soon" lamp to come on, or set trouble codes in the ECM memory. These intermittent conditions usually result in driveability complaints and cause trouble codes to be set in the ECM memory without turning on the indicator lamp, or are "read" as intermittent trouble codes when testing the system with the SCAN type tester. However, trouble code diagnosis charts cannot be used to diagnose this type of malfunction as a fault must be present in order to be located using the charts, and use of the charts to diagnose an intermittent condition may result in unnecessary replacement of components.
Most intermittent malfunction conditions are caused by poor electrical or vacuum hose connections, or defective or improperly routed wiring or hoses. The cause for most intermittent malfunctions can usually be located by performing a thorough visual inspection of the system vacuum and wiring harnesses and/or by road testing the vehicle while monitoring the suspected circuit with suitable test equipment. After performing the "Diagnostic Circuit Check" and ensuring that the indicator lamp is operating and that no "hard" codes are set in the ECM memory, use the following procedure to locate intermittent malfunctions:


1. Inspect vacuum hoses for splits, kinks and proper connection, and ensure that hoses are routed properly.
2. Inspect fuel system components for proper mounting, fuel, air or vacuum leaks, and correct as needed.
3. Inspect secondary ignition wiring and replace any wires that are burned, cracked or broken.
4. Inspect engine compartment and emission control system wiring and repair or replace wiring that is broken chafed or damaged.
5. Inspect electrical connectors noting the following:
a. Ensure that terminal is making proper contact with wire by removing terminal from connector and inspecting for proper crimping and broken wire strands.
b. Ensure that all terminals are fully seated in connector.
c. Ensure connector terminals are not damaged or deformed, and carefully reform terminals in connectors of suspected circuits to increase spring tension.
d. Ensure connector halves are properly mated and fully seated.
6. Inspect indicator lamp and ALDL connector wiring for shorts to ground and repair as needed.
7. Check continuity between proper terminals of ECM connector and engine ground, and repair wiring if no continuity exists.
8. Check for electrical interference caused by defective relays, ECM driven solenoids or switches, and secondary ignition system components, as they may cause voltage surges.
9. Ensure that EST wiring is properly routed and insulated from distributor wiring, distributor, ignition coil and alternator.
10. Inspect added accessories such as lights, two-way radios etc. for proper installation, ensuring that no accessories are patched into engine control system wiring.
11. Ensure diodes and resistors installed across accessories such as the A/C compressor clutch are not open.
12. Connect SCAN tool following manufacturer's instructions, or connect suitable voltmeter to suspected circuit and road test vehicle, noting any abnormal readings and the conditions under which they occur. Abnormal readings indicate that the tested circuit may be cause for malfunction.


plus a great link on using multimeters
http://www.fluke.com/application_not...AGID=1&SID=103

Bill

 

this chart is a great help elcamino , i'am going to get started at this, and i will post back!

 

well i followed the chart and every thing seems to check out, also what i did was remove the rubber boot at the connection between the harness and the o2 to try and get a little more depth on the plug and things are lookin better already, it goes into closed loop and stays there and the o2 mv appear to be operating properly about 90 mv at idle and up to 1v depressing the throttle. the car is hot now and i will do another scan at a cold start!

 

do you have a cat on your car? I get the same code when my car warms up and dosent go into closed loop. My tech tells me theat with no cat, the o2 sensor dosent get hot and sends a faulty reading. I will be checking to see if i have a t-stat also and as well as putting my cat. convertor back on.

 

sorry to double post but where can i find ckt 413 o2 ground (tan) i would like to check this ground.

 

No, i do not have a cat on, there is alot of people on this board that don't have a cat and i don't think not having a cat is the problem, i just ran the car for about 20 minutes at idle and it stayed in closed loop, mybe Elcamino can shed some light on this one. I like this guy he has all the braines when it comes down to this stuff!

 

Sorry to wait soo long to post a reply.

First off, I've been checking for the location of circuit 413. Its apparent that GM thinks that this info is classified as Top Secret. I was finially able to get somewhat of a wiring diagram for it. See bottom. Its part of your engine ground. You may have to follow it back from the Ecm or get lucky and follow it from what looks to be the main ground.

Secondly, some have retro-ed a heated O2 into thier system for three reasons. Poor grounding, Heating O2 when using headers and quicker heat-up of the O2 sensor.

(IMO) If your not running a cat you really need to install one of these in your car to get the sensor up to operating temp.

Here's a couple of good links, after readingyou'll understand:
http://sethirdgen.org/HO2S.htm
https://www.thirdgen.org/techbb2/sho...=wire+heatedo2

Bill

 

Thanks Elcamino on the great info. I currently have a test pipe in the location of the cat , it has flanges on both sides , i also have a brand new cat that has flanges , i can swap it in and see what happens won't be to big of a job, evey time i go for my (aircare) test i swap the cat back in. i think that there is a very good chance this is a temperture issue with the o2.

 

told ya:lala:

 

sorry for the late reply , ok this is what i did, i checked the voltage at ckt 412 at the ecm side down by the o2 plug with the ignition on engine off and i have .876 mv. according to this chart it is suposed to be any were from .3 to .6 mv . this chart says that there is an open or bad connection or faulty ecm , so i probed the wires at D6 and D7 at the ecm and i have the same .876 mv i checked the connections at the ecm , every thing looks clean. the funny thing is some times the car at idle will go into closed loop and i will check it with my dvm and it will read .323 mv , then i will rev the motor for about 20 to 30 seconds and it will go back into open loop and i will check the voltage at the o2 plug on the ecm side and it's back to the .876 mv . i think the ecm is bad what do you guys think!

 

Check out my post in the link below even though its about a MAF problem, after you read it you'll understand:
https://www.thirdgen.org/techbb2/sho...20#post1902220

I found that GM was having problems with the 89's & 90's with the same Ecm as the 88's as far back as Aug 1991. It seems this Ecm likes to crack solder joints on the circuit board. So its very possible that your Ecm is in fact inneed of replacing. I would get a good quality reman from like CarQuest or NAPA. If you go to Auto(ripoff) Zone I'll shoot you myself CarQuest and NAPA sell good quality products and stand behide them, unlike others.

Afterward taking care of the Ecm, I would still put in that heated O2.

Good Luck
Bill

 

Hi Bill, i ordered a new (ecm) but it won't be here until monday and i will post back after i test it. Thanks for your help!