Progress Thread Nasty Ninety Notch

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Did you replace the 02 harness at all? It HAS to be for a 90
I replaced it with LRS-8793XSHM from Late Model Restoration. It says 91-93 for manual transmission. I do know that it only allows the correct 5 volts to the ECM as opposed to the harness for autos which allow 12 volts and will fry a manual ECM. Don't ask me how I know that. I assume you are addressing the O2 related codes.

What do you think?
 
Okay, there is a difference between manual harnesses from 88-93. I'll upload a pdf incase anyone else has an issue. So, no. a 91-93 manual harness will not work properly in a 90. Thanks to hoopty5.0 for alerting me.

My O2s are only coming on at 2k rpms. Maybe its due to the wrong pin configuration. I'll change it and let you know.
 

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  • 88-93 O2 Wire Config for all Years.pdf
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Did you replace the 02 harness at all? It HAS to be for a 90
Ok. I checked the harness pigtail for the proper jumper sequence for a 1988 (CA)-1990. It was jumpered correctly (i.e., 1 & 5).

Next, I disconnected both O2s, turned the car on, and checked the grey wire with a DVM. From what I understand, there should be 12v there in order to heat the O2s, but the meter read no higher than mV on either side. Thoughts?
 
Ok. I checked the harness pigtail for the proper jumper sequence for a 1988 (CA)-1990. It was jumpered correctly (i.e., 1 & 5).

Next, I disconnected both O2s, turned the car on, and checked the grey wire with a DVM. From what I understand, there should be 12v there in order to heat the O2s, but the meter read no higher than mV on either side. Thoughts?
Man I wish I could help you on the pinouts, but I've offered up all the information I have. @jrichker could probably shed some light on it for you.
 
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Update: Codes, Yuck!

KOEO = none
Continuous Memory =
41 HEGO sensor voltage low / system lean (and/or) No HO2S switching detected.
91 HEGO sensor signal out of range /always lean.
96 Fuel pump secondary circuit / high speed fuel pump relay open.

Interestingly, my O2 sensors have less that 100 miles on them. As for code 96, I'm not exactly sure what's wrong. The fuel pump seems to work fine. Any thoughts?

I cannot get any KOER codes until Continuous is fixed because they could be invalid.
If @jrichker doesn't come into your thread to help you then I would post this in the tech area where he spends a lot of his time (or so it seems to me). Best of luck!
 
If you didn't get a code 67, there is no reason why you can't get accurate engine running codes. Code 67 prevents you from getting the engine running codes. Dump the codes and try again.

The O2 sensor harness is the same from 88-93. The qualifier is that Auto transmission O2 sensor harnesses are different from manual transmission harnesses.


The green/yellow wire is the 12 volts for the O2 sensor heater, the black/gray wire is the signal & heater power ground, other wire is the O2 sensor output. The sensor wiring is Teflon insulated to survive the high heat around the exhaust system. Use regular insulated wire on the O2 sensors and the heat from the exhaust will melt or damage the wire's insulation.

[
%20.gif
he numbers on the sensor body match the numbers on the sensor socket. That shows you what wires are the heater, ground and sensor outputs.

60 is the sensor and heater ground. It terminates up in the engine fuel injector harness with an orange wire that bolts to either the back of the cylinder head, intake manifold or car body. Make sure this is grounded if you want the O2 sensors to work correctly.

90 (dark brown/lt green)& 94 (dark green/Purple) are the O2 sensor outputs.

687 is the 12 volt O2 sensor heater power that connects to a fuse link in the wiring harness. There is a fuse link for the O2 sensor heater power. According to Ranchero50, it is in the wiring near the passenger side hood hinge. Measuring the voltages will give a clue if it has shorted to the O2 sensor signal lead. The O2 sensor voltage should switch between .2-.9 volt at idle.

The diagram for the O2 sensor harness is below:
Diagram courtesy of Tmoss & Stang&2birds

mustango2harness-gif.555758


88-91_5-0_eec_wiring_diagram-gif.555759


fox-5-0-o2-sensor-drawing-jpg.595636



Originally Posted by 302EFI [/b]

Revised 16-Oct-2011 to add O2 sensor harness warnings
The wires for the 02's and low oil did not change throughout the years, they are all in the same place.
The main ones you need to worry about are (on the harness end (ECU) that plugs into the 02 plug) is:
\- 1. Lightblue / yellow
- 2. White / Purple
- 3. Purple / Yellow
The White/Purple & Purple/Yellow gets looped for a automatic ECU
The Purple/Yellow & Lightblue/Yellow for a manual ECU

View attachment 555761
Not all wires are shown for clarity and simplicity

See http://forums.corral.net/forums/gen...manual-auto-differences-year-differences.html for more O2 sensor wiring harness info

Basic premise to use with transmission swaps:
Only run a 5 speed trans O2 harness with an A9L. Do not run an Auto O2 sensor harness with an A9L. Doing so will damage the computer’s internal signal ground.
Only run an Auto trans O2 sensor harness with an A9P in a car that has an Auto trans. Using a 5 speed trans O2 sensor harness with an Auto trans will cause no crank problems.
See http://www.stangnet.com/mustang-forums/749974-computer-issue.html#post7490537 for Joel5.0’s fix to the computer internal signal ground.
The 4 cylinder O2 harness uses 4 wire O2 sensors. It won’t work correctly without modifying it.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/91-93_5.0_EEC_Wiring_Diagram.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

TFI module differences & pinout
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif

Fuse box layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif
?temp_hash=be118ae297e65d67e3deef9f3d54e77f.gif
mustangO2Harness.gif
88-91_5.0_EEC_Wiring_Diagram.gif
 

Attachments

  • Fox 5.0 O2 sensor drawing.jpg
    Fox 5.0 O2 sensor drawing.jpg
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If you didn't get a code 67, there is no reason why you can't get accurate engine running codes. Code 67 prevents you from getting the engine running codes. Dump the codes and try again.

The O2 sensor harness is the same from 88-9.3 The qualifier is that Auto transmission O2 sensor harnesses are different from manual transmission harnesses.


The green/yellow wire is the 12 volts for the O2 sensor heater, the black/gray wire is the signal & heater power ground, other wire is the O2 sensor output. The sensor wiring is Teflon insulated to survive the high heat around the exhaust system. Use regular insulated wire on the O2 sensors and the heat from the exhaust will melt or damage the wire's insulation.

?temp_hash=be118ae297e65d67e3deef9f3d54e77f.gif

The numbers on the sensor body match the numbers on the sensor socket. That shows you what wires are the heater, ground and sensor outputs.

60 is the sensor and heater ground. It terminates up in the engine fuel injector harness with an orange wire that bolts to either the back of the cylinder head, intake manifold or car body. Make sure this is grounded if you want the O2 sensors to work correctly.

90 (dark brown/lt green)& 94 (dark green/Purple) are the O2 sensor outputs.

687 is the 12 volt O2 sensor heater power that connects to a fuse link in the wiring harness. There is a fuse link for the O2 sensor heater power. According to Ranchero50, it is in the wiring near the passenger side hood hinge. Measuring the voltages will give a clue if it has shorted to the O2 sensor signal lead. The O2 sensor voltage should switch between .2-.9 volt at idle.

The diagram for the O2 sensor harness is below:
Diagram courtesy of Tmoss & Stang&2birds

mustangO2Harness.gif

88-91_5.0_EEC_Wiring_Diagram.gif
nsor wiring is the same for 87-93 5.0 Mustangs [/b]
View attachment 555760 ication

Originally Posted by 302EFI [/b]

Revised 16-Oct-2011 to add O2 sensor harness warnings
The wires for the 02's and low oil did not change throughout the years, they are all in the same place.
The main ones you need to worry about are (on the harness end (ECU) that plugs into the 02 plug) is:
\- 1. Lightblue / yellow
- 2. White / Purple
- 3. Purple / Yellow
The White/Purple & Purple/Yellow gets looped for a automatic ECU
The Purple/Yellow & Lightblue/Yellow for a manual ECU

View attachment 555761
Not all wires are shown for clarity and simplicity

See http://forums.corral.net/forums/gen...manual-auto-differences-year-differences.html for more O2 sensor wiring harness info

Basic premise to use with transmission swaps:
Only run a 5 speed trans O2 harness with an A9L. Do not run an Auto O2 sensor harness with an A9L. Doing so will damage the computer’s internal signal ground.
Only run an Auto trans O2 sensor harness with an A9P in a car that has an Auto trans. Using a 5 speed trans O2 sensor harness with an Auto trans will cause no crank problems.
See http://www.stangnet.com/mustang-forums/749974-computer-issue.html#post7490537 for Joel5.0’s fix to the computer internal signal ground.
The 4 cylinder O2 harness uses 4 wire O2 sensors. It won’t work correctly without modifying it.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/91-93_5.0_EEC_Wiring_Diagram.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

TFI module differences & pinout
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif

Fuse box layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif
That's awesome! I'm also a bit overwhelmed and lost. What do you suggest I check?

Thank you.
 
Start at the top and work your way to the bottom. That way, you will have looked at all the possibilities and not miss the second or third item that might be incorrect
I'll do my best. I'll attach some pics of, I think, related Fuse Links. I'd like to see what you think. I think the 20 GA connected to the solenoid might be related to the lack of 12v to the O2s. The other is what I believe to be the ECM ground.
20 GA Link 1.jpeg

20 GA Link 2.jpeg


ECM Ground 1.jpeg



ECM Ground 2.jpeg

Overall Pic...
Overall.jpeg
Zoom in to link bundle...
Link Bundle.jpeg

I'll see about following your list tomorrow and let you know. Thoughts on pics?
 
I'm an electrical idiot. How do I check continuity? What should the reading be? What ground wire?


Ah.... Do you possess a multi-meter?

If not, we need to begin with you getting your hands on one or buying a cheap one then watching a couple youtube videos.

You will also need a crimper, a wire stripper, and soldering iron. Probably a few connectors too.

There's some rambling in this but otherwise:


View: https://youtu.be/TdrU38edY8M
 
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64326d1287785504-fusible-link-burned-up-need-help-87-93-5.0-mustang-fuse-links.gif


The picture below shows the common ground point for the battery , computer, & extra 3G alternator ground wire. A screwdriver points to the bolt that is the common ground point.

The battery common ground is a 10 gauge pigtail with the computer ground attached to it.
Picture courtesy timewarped1972
ground.jpg


Correct negative battery ground cable.
86-93-mustang-oem-style-ground-cable-gif.56567


The third picture you posted is the engine control computer ground. It is the second most important ground it the whole car.
The computer's main power ground (the one that comes from the battery ground wire) uses pins 40 & 60 for all the things it controls internally: it comes off the ground pigtail on the battery ground wire. Due to its proximity to the battery, it may become corroded by acid fumes from the battery.
In 86-90 model cars, it is a black cylinder about 2 1/2" long by 1" diameter with a black/lt green wire.
In 91-95 model cars it is a black cylinder about 2 1/2" long by 1" diameter with a black/white wire.
You'll find it up next to the starter solenoid where the wire goes into the wiring harness.

All the grounds need to bolt to clean, shiny bare metal. A wire brush or some fine sandpaper is the best thing to use to clean the ground connections.
 
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Ah.... Do you possess a multi-meter?

If not, we need to begin with you getting your hands on one or buying a cheap one then watching a couple youtube videos.

You will also need a crimper, a wire stripper, and soldering iron. Probably a few connectors too.

There's some rambling in this but otherwise:


View: https://youtu.be/TdrU38edY8M

I have access to all those supplies. My landlord lets me use his. He is an electrician. He doesn't necessarily have the time to help me diag, but I can use his stuff.
 
Ok. I have a lot to look at and digest. I really appreciate all the help you guys are providing.

jrichkter, I'm trying not to get info from multible sources because it can be confusing. However, I do have a question:

Regarding the 41 & 91 codes and the possibility of the O2s not heating up properly or at all, do you see merit in the theory that "Fuse Link J," which is a blue 20GA link which comes off of the ignition switch's A2 terminal, could be faulty? Maybe that's what's going on? This is a pain fuse link inside the dash.

Anyhow, I'm thinking that a logical plan of action is to:

1) Make sure ECM ground is good.
2) Follow your diag list for 41 & 42.

Agree?
 
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The fuse link for the O2 sensor heater is over by the passenger side hood hinge bracket from what I have been told. You will have to unwrap some of the plastic tape that covers up things to get to the fuse link.

The blue 20 gauge fuse link is for the ignition coil & ECC control relay.

Diagram courtesy of TMoss & Stang&2Birds
fuel-alt-links-ign-ac.gif


Your #1 & then #2 plan is right on target; stick with it.
 
The fuse link for the O2 sensor heater is over by the passenger side hood hinge bracket from what I have been told. You will have to unwrap some of the plastic tape that covers up things to get to the fuse link.

The blue 20 gauge fuse link is for the ignition coil & ECC control relay.

Diagram courtesy of TMoss & Stang&2Birds
fuel-alt-links-ign-ac.gif


Your #1 & then #2 plan is right on target; stick with it.
If the location for the O2 link is as you say, then I can take a deep breath after the punch in the gut (i.e., removing dash to get to link). I don't mind unwrapping tape, especially compared to removing the dash. That's been done already (earlier in build post).

Thank you for the info.