FI / Sensors Harness vs Sensors

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Bob Weir
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FI / Sensors Harness vs Sensors

Post by Bob Weir »

FI / Sensors Harness vs Sensors

Next time you suspect a sensor or get a code, you might want to consider the wiring harness.

I opened 2 Fuel Injection / Sensor harnesses. Obviously the frayed wires in the “sensors” section are not going to make a proper connection, especially for the TPS [Throttle Position Sensor].

Around Sep 1995 Ford TSB instructs to use a new connector with “gold plated” clips. Part # E9RZ-9B989-C. Apparently Ford felt this a necessity for correct current flow.

Image

I also realized two differences in a harness from an 88 to another from an 89. The ground wiring is different and more obvious is the connectors to the main harness. The 88 has a male plug while the 89 has a female plug in FI / Sensors Harness. No mixing and matching here!
Image

Below is the 89 harness. It has a different Br splice for Water Temp Sensor with TPS.

Image

Both harnesses have the gray connector for 2 Bk wires on one end and 2 Br/Y wires on the other end.

Here’s the FI / Sensors Harness pin out:

Connector pin structure:
A row:
Br - 2, 3 & 5 Fuel Injectors
Br/Bk - 1, 4 & 6 Fuel Injectors
Bk - Idle Air Solenoid aka IAS.
Br/Y - IAS

B Row:
Br/Gr - Water Temperature Sensor [to EEC],
Br - Water Temperature Sensor [to EEC] and TPS pin 46 Signal Return [OEM splice in the harness]
Br/Gr - TPS pin 47 Throttle Position
Br/Bk Throttle Position Sensor aka TPS pin 26 VREF

Water Temperature Sender [to gauge] is a separate Br ground outside this harness.

What started my adventure into harness stripping…
In this case, my Scorpio developed a serious erratic idle and showed Code 63 [low voltage to TPS]. NOS Motorcraft TPS installed and code remained. Redid a few grounds as recommended my fellow Merkur owners that resulted in better performance, but Code 63 continued. I did all the workshop tests in “D” [Throttle Position Sensor] and “C” [Voltage Check]. I also have the “88” wiring schematic, Workshhop Manual as well as the “89” Elec & Vac Manual. Traced and jumped every wire I could. A few results were not to spec by the book. Ex 5.03 v vs 4.0 and others at 200k weren’t moving the ohm meter. I blamed misprint, inaccurate multimeter and even operator error and kept testing.

Your comments and especially corrections are appreciated. Thanks to everyone who helped me through this frustrating situation.
Last edited by Bob Weir on Sat Jul 26, 2014 10:45 am, edited 2 times in total.
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Re: FI / Sensors Harness vs Sensors

Post by Bob Weir »

Update

Reference Workshop Manual page 4-21 Electrical Schematic.

EEC pin 46 Brown wire is common to "6" sensors! HEGO, ECT, TPS, ACT, MAP and PFE.

In the first pik, the 2 Br wires are spliced together under black tape. This is OEM! The Br wire > connector > tape out under battery > EEC. I seriously suspect the TPS & ECT splice due to the engine's heat and movement. I suspect a short here could affect all the connected sensors.
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Re: FI / Sensors Harness vs Sensors

Post by Father Adam »

I'd be interested to know what code reader you have Bob, I bought a Gunson one last year but it's for the later Ford models and so has a slightly different connector to mine (still 3 pin though).
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Re: FI / Sensors Harness vs Sensors

Post by Ed Lijewski »

Descartes: "Cogito Ergo Sum"
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Re: FI / Sensors Harness vs Sensors

Post by Bob Weir »

Father
I use a INNOVA #3145 for OBD 1. that displays the code #s. For Ford only 1981 - 1995. Cheep & simple to use. Comes with book of instructions and code # & their descriptions. I started with an Actron, but u have to count audible beeps = PIA.
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Re: FI / Sensors Harness vs Sensors

Post by Father Adam »

This Gunson one I have is one that you have to count the number of flashes too, one with a display would make life easier for me.

Tell me though Bob, would this type of reader tell me which ABS sensor is kaput?

:cheers
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Re: FI / Sensors Harness vs Sensors

Post by Bob Weir »

The INNOVA #3145 for OBD 1 only does engine EEC management. Well worth its cost. My best guess on the is the Rotunda and ABS adapter as mentioned in the workshop manual. I often wanted to borrow one.
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Re: FI / Sensors Harness vs Sensors

Post by Father Adam »

Thank you Bob!

:cheers
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Re: FI / Sensors Harness vs Sensors

Post by Bob Weir »

Since I'm not buying into Photobucket's extortion, I'm trying to replace some photos. Here's a few for this post.
FI Harness connector v1.jpg
FI Harness connector v1.jpg (48.4 KiB) Viewed 9726 times
FI Harness connector v2.jpg
FI Harness connector v2.jpg (51.64 KiB) Viewed 9726 times


"FI Harness ng r1.jpg" shows the terrible condition of the wires to the Throttle Position Sensor and other sensors.

NOTE This is the condition of the wires in a Scorpio. You can imagine what the heat of a Turbo could be doing to an XR's wiring. :shock:
FI Harness ng r1.jpg
FI Harness ng r1.jpg (46.73 KiB) Viewed 9726 times
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Re: FI / Sensors Harness vs Sensors

Post by Nolan04 »

Bob Weir wrote: Thu Jul 17, 2014 12:14 am FI / Sensors Harness vs Sensors

Next time you suspect a sensor or get a code, you might want to consider the wiring harness.

I opened 2 Fuel Injection / Sensor harnesses. Obviously the frayed wires in the “sensors” section are not going to make a proper connection, especially for the TPS [Throttle Position Sensor].

Around Sep 1995 Ford TSB instructs to use a new connector with “gold plated” clips. Part # E9RZ-9B989-C. Apparently Ford felt this a necessity for correct current flow.

Image

I also realized two differences in a harness from an 88 to another from an 89. The ground wiring is different and more obvious is the connectors to the main harness. The 88 has a male plug while the 89 has a female plug in FI / Sensors Harness. No mixing and matching here!
Image

Below is the 89 harness. It has a different Br splice for Water Temp Sensor with TPS.

Image

Both harnesses have the gray connector for 2 Bk wires on one end and 2 Br/Y wires on the other end.

Here’s the FI / Sensors Harness pin out:

Connector pin structure:
A row:
Br - 2, 3 & 5 Fuel Injectors
Br/Bk - 1, 4 & 6 Fuel Injectors
Bk - Idle Air Solenoid aka IAS.
Br/Y - IAS

B Row:
Br/Gr - Water Temperature Sensor [to EEC],
Br - Water Temperature Sensor [to EEC] and TPS pin 46 Signal Return [OEM splice in the harness]
Br/Gr - TPS pin 47 Throttle Position
Br/Bk Throttle Position Sensor aka TPS pin 26 VREF

Water Temperature Sender [to gauge] is a separate Br ground outside this harness.

What started my adventure into harness stripping…
In this case, my Scorpio developed a serious erratic idle and showed Code 63 [low voltage to TPS]. NOS Motorcraft TPS installed and code remained. Redid a few grounds as recommended obtenir crédit my fellow Merkur owners that resulted in better performance, but Code 63 continued. I did all the workshop tests in “D” [Throttle Position Sensor] and “C” [Voltage Check]. I also have the “88” wiring schematic, Workshhop Manual as well as the “89” Elec & Vac Manual. Traced and jumped every wire I could. A few results were not to spec by the book. Ex 5.03 v vs 4.0 and others at 200k weren’t moving the ohm meter. I blamed misprint, inaccurate multimeter and even operator error and kept testing.

Your comments and especially corrections are appreciated. Thanks to everyone who helped me through this frustrating situation.
OK, thank you very much for your share :)
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Re: FI / Sensors Harness vs Sensors

Post by Bob Weir »

Welcome to the MCA
Introduce yourself to the members.
Here’s the link > http://forum.merkurclub.com/forum/viewforum.php?f=19
Also, Click on your username / User Control Panel / Profile =>
Ed Lijewski
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Re: FI / Sensors Harness vs Sensors

Post by Ed Lijewski »

"What started my adventure into harness stripping…
In this case, my Scorpio developed a serious erratic idle and showed Code 63 [low voltage to TPS]. NOS Motorcraft TPS installed and code remained.
Redid a few grounds as recommended my fellow Merkur owners that resulted in better performance, but Code 63 continued. I did all the workshop tests in “D” [Throttle Position Sensor] and “C” [Voltage Check]. I also have the “88” wiring schematic, Workshhop Manual as well as the “89” Elec & Vac Manual. Traced and jumped every wire I could. A few results were not to spec by the book. Ex 5.03 v vs 4.0 and others at 200k weren’t moving the ohm meter. I blamed misprint, inaccurate multimeter and even operator error and kept testing."

Commendable investigation Bobolino!👏

A new TPS (gold plated pigtails) wouldn't likely clear Code 63 which points to low voltage delivered at the TPS. Given what you found in the opened harness one would expect that repairing/replacing the section of questionable wiring would make a difference. But this thread doesn't report about that, other than checking/cleaning grounds (which I doubt would resolve erratic idle issue). So did you ever find and resolve the source of the Code 63?

YMMV
Last edited by Ed Lijewski on Fri Apr 10, 2020 8:13 pm, edited 1 time in total.
Descartes: "Cogito Ergo Sum"
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Bob Weir
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Re: FI / Sensors Harness vs Sensors

Post by Bob Weir »

Hi Ed

Good to "talk with you".

I finally did cure the problems. But I don't remember what repair was the final cure. The FI harness was definitely a help, but the real cause was a bad EEC. Dimitri gave me the suggestion. I opened the ECC case and it was obvious - a burnt "what'd u call it". I don't know if the wiring harness screwed up the EEC or visa versa.

Something recently caused me to do a search on "fusible links". Now I know the difference. Fortunately, I did it right when I fixed mine. Go to this thread you made comments on...
viewtopic.php?f=30&t=36551&p=318628#p318516
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