2004 Sport Trac Head Unit replacement. Lots of questions about how to do this. | Ford Explorer Forums - Serious Explorations

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2004 Sport Trac Head Unit replacement. Lots of questions about how to do this.


December 20, 2009
Reaction score
City, State
Houston TX
Year, Model & Trim Level
2004 SportTrac 4x4

I have reviewed the above wiring diagram and the harness documentation for a Metra 70-1771 and a lot of things do not make much sense. tjtheman007 also did a good write-up in this thread and I looked that over too.

I have not taken delivery of the 2004 Sport Trac yet but I know it has the Pioneer 6 disc changer and an amp behind the rear seat. Unlike tjtheman007, I sure mine does NOT have MP3 player on it so I don't know if this qualifies as the Adrenaline version. Its just a 6 disc changer and pretty basic looking, ford styling front plate.

Crutchfield tech support indicates that the Metra 70-1771 install strategy ignores the OEM sub-woofer and sub-woofer amp which seems lame and just run front speaker wires to the new head-unit. I should be able to tie into it like tjtheman007 did with the RCA line-level jacks.

Questions -

What is going on in this wiring diagram with the front left and right speakers? It shows one pair driven by the head unit and another pair driven by the subwoofer amp and they are all the same colored wires.

Both Fredness and tjtheman007 appeared to only use line-level outputs from the new head unit and the factory OEM subwoofer amp to drive the front speakers. That makes perfect sense to me but why did Ford do it differently? Crutchfield strategy also makes sense as the Kenwood DPX502BT HU is probably a better amp than factory.

The link to the Metra 70-1771 has a couple undocumented wires. The black/orange is undocumented and crutchfield tech-support indicated that it was no longer included with the unit as it was un-used. The black with white stripe is also undocumented in the wire chart and Crutchfield tech-support indicates its for an amp ground.

The PDF wiring diagram shows a pair of undocumented wires between the head unit and the amp. On the head unit they are PIN 1 RED/BLK (-) and PIN 2 BRN/ORG (+) . On the amp the same colors plug to PIN 1 - and PIN 8+. Is PIN 8 BRN/ORG where the +5V signal is supposed to go? Crutchfield did not include the 12V/5V converter in the recommended hardware although they do sell it for $20 as they bypass the amp altogether. Or is 1 & 8 a line-level subwoofer signal? This thread for a '98 suggest as much although the polarities are reversed between the thread and the wiring diagram.

tjtheman007's head unit appears to have 6 RCA jacks. FL, FR, RL, RR for mids and highs and a pair for subwoofer L/R but he only chose to wire one of the sub-woofer signals. Why?

Final question. I am not an audiophile of any sort; I am pretty tone deaf. Assume I do wire in this sub-woofer amp in through the RCA line-level outputs. What is a recommended cut-off frequency from the head unit for this Ford/Pioneer amp and subwoofer?

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Part 1 solved. The wiring diagram is fiction and bares no resemblance to what is actually in the vehicle.



The subwoofer amp has a 10 pin connection as follows

Vio/Blu  constant hot.
Blk/Grn GND
Grn/Vio purpose unknown
Red/Blk purpose unknown
Brn/Org purpose unknown

I can presume that of the unknowns, one is a ON signal when the head unit gets power and the other two are actual music signals + and -.

On the HU I have a corresponding 8 pin connector that matches with
  1. Brn/Org
  2. Red/Blk
  3. Blk (not Blk/Grn)
  4. Grn/Vio
  5. empty
  6. empty
  7. empty
  8. empty
I am going to speculate based on the wiring diagram and the pinout from the HU that Grn/Vio is the on signal (12V or 5V TBD), that Red/Blk is the (-) signal and Brn/Org is the (+) signal for mono subwoofer. I was unable to figure out which was the ON signal mostly because my multi-meter probes are too fat and the HU was disconnected when I checked the voltages.

The Metra 70-1771 16 pin connector did NOT fit my vehicle at all. The pin count was wrong and the Metra pins were space far apart while the vehicle's were much closer together. I was hoping that the connector would fit and that I could get a better sense of what these wires were for, for this post. I will be calling Crutchfield to get the right connector.

At the Ford HU I have a 6 disc changer with the following per the pinouts. The pinouts numbers are only on the MAIN wiring harness. There is a 5-6 inch extension from the main wiring harness to the HU and the wires change colors. On the main wiring harness they are

[ 1] Grn/Vio Constant hot
[ 2] Wht/Vio (RUN +)
[ 3] Red/Blk (lighting or START detect)
[ 4] Blk (GND maybe)
[ 5] empty
[ 6] empty
[ 7] empty
[ 8] Org/Grn (LF+)
[ 9] Gry/Blu (LR+)
[10] Org/Red  (RR+)
[11] Wht/Grn (RF+)
[12] Grn/Org (RF-)
[13] Blk/Grn  GND opposite pin 1
[14] empty
[15] Red/Blk (lighting or START detect)
[16] empty
[17] empty
[18] empty
[19] empty
[20] empty
[21] Blu/Wht (LF- if LT BLU)
[22] Brn/Yel (LR- I guess it could be tan instead of brown)
[23] Brn/Pnk (RR-)
[24] empty

My sense of color is far from perfect and some of the wires it looked like there were two stripes so it was hard to distinguish a solid color from a stripe. Items in () are assumptions based on the wiring diagram colors but not pin position. It is curious/strange that pins 11/23,10/22, 9/21, 8/20 would logically be paired in the harness but the wiring choices assumed above are offset by one position.

I haven't received the replacement kit but the wiring diagram for the Metra 70-5521 matches this noting that PIN 4 (black) is not broken out and that PIN 5 is broken out for a power antennae that I don't have. PIN 3 Lighting pairs with PIN 3 illumination but no corresponding function on the HU. I wonder what PIN 4 is for. PIN 15 is also not broken out by the METRA adapter and the HU has no corresponding START detect capability. I have not really noticed if the OEM radio cuts out when I turn the key to start. I have noticed that it does NOT come on when I turn the key to ACC which is annoying and feels funny like ACC is not fully engaged (EDIT: It does cut out on start and I recall that on my 2002 Sport Track, ACC did turn on the radio). ACC being past off is also slightly annoying.

The 70-5521 also has an 8pin subwoofer/woofer harness. Pin1,2 Match with the WHITE subwoofer and would correspond with BRN/ORG (+) and RED/BLK (-). These wires are only marked as +,- on the wiring diagram but now they appear to be signal wires. Its slightly strange that on the Ford connectors the pins are marked 1-12, then 13-24 and 13 is opposite 1. On computer cables they usually wrap-around on a pinout and 13 would be opposite 12 and 1/24 would be opposite. If the wiring diagram was using computer style numbering, 1 and 8 would be opposite and likely support a common function. Pin 3 is not broken out and is Blk on the vehicle. This might be a problem. I don't recall if the HU was plugged in or not when I was finding the GND on the amp. If the amp is grounded thru the OEM HU then I will need to body ground that wire which is what is recommended in the Kenwood install guide. PIN 4 BLU/WHT would then be the ON signal wire (presumably at 5V) and match the GRN/VIO pair in the vehicle. The Metra Kit marks white as SubWoofer and RED as WOOFER while my HU marks WHITE as Left and RED/Right.

This main wiring harness then plugged into an unnumbered 5 inch extension cable that went to the head-unit. I matched the wires for the pin numbers. Again my probes were OK for the larger holes that supplied constant hot and GND ( or I matched from the main wiring harness but I was unable to find a switched/run hot.
  1. Yel Constant HOT
  2. Red
  3. Blu
  4. Pnk
  5. Yel/Wht (this one was hard to make out any colors)
  6. Blk/Gry
  7. Gry/Wht
  8. Wht
  9. Grn
  10. Vio
  11. Gry
  12. Gry/Blk (end of row)
  13. Blk GND
  14. empty
  15. Red/Blk
  16. empty
  17. empty
  18. empty
  19. empty
  20. empty
  21. Blu/Wht
  22. Brn/Yel
  23. Brn/Pnk
  24. empty



Crutchfield tech support is now recommending a Metra 70-5521. The pin count is right and the owner's manual diagram looks about right. Should arrive by Tuesday. I am curious if the Metra will plug into both the main wiring harness and the extension. I did not take a good picture but from the ones I have, they look the same.

Mapping the effect of the Metra 70-5521 wiring harness

[01] Grn/Vio -> Yel           Constant (+)
[02] Wht/Vio ->  Red          Switched (+)
[03] Red/Blk -> Org           Illumination Control
[04] Blk -> empty
[05] empty -> Blu              Power Antenna
[06] empty
[07] empty
[08] Org/Grn -> Wht            LF+
[09] Gry/Blu -> Grn            LR+
[10] Org/Red -> Vio            RR+
[11] Wht/Grn -> Gry            RF+
[12] Grn/Org -> Gry/Blk        RF-
[13] Blk/Grn -> Blk            Gnd
[14] empty
[15] Red/Blk -> empty         Probably start detect
[16] empty
[17] empty
[18] empty
[19] empty
[20] empty
[21] Blu/Wht -> Wht/Blk        LF-
[22] Brn/Yel -> Grn/Blk        LR-
[23] Brn/Pnk -> Vio/Blk        RR-
[24] empty

Then the SubWoofer 8 pin connector maps as
[01] Brn/Org -> Wht       RCA White Sub +
[02] Red/Blk -> Blk       RCA White Sub -
[03] Blk -> empty
[04] Grn/Vio -> Blu/Wht    Sub Turn on via an Blu/Red attached to the 12V to 5V Transistor 120AFDI5V
[05] empty -> Red          RCA Red +
[06] empty -> Blk          RCA Red -
[07] empty -> empty
[08] empty -> Blu/Wht      Woofer Turn on



I understand why Ford might want to direct supply a larger constant hot and ground to the OEM head unit. I dont understand why they would feed that back into the harness though. I ended up just storing this extension cable back behind the climate controls as the Metra/Kenwood harness provided more than enough length.


The Kenwood is significantly taller than the OEM Pioneer 6 disc changer and requires that the top of the panel to be cut down. I dont think this would interfere with putting the original back in as the Ford HU has a pretty deep faceplate that would cover up what was cut out and the sides of the panel are what actually hold the unit in place



I used a Dremel cut-off wheel to trim the plastic. The directions say to leave as much as possible top and bottom that will still allow a fit but I found that cutting it all the way to flush was necessary.



The Metra 95-5817 Kit includes two side mounting pieces and a thin bottom piece to fill in any gaps. The bottom piece appears to want to snap into the side pieces but fits poorly for that. Its just friction holding it in. I had a small gap at the top but with the visual lines from the cab its not really possible to see it.



Wiring harness that I connected into and a mounting bar that I had to remove. I stored the extension and the removed bar back behind the climate control knobs where their is plenty of space. I mounted the microphone on top of the steering column and was able to fish the wire in the gap between the instrument cluster and the rest of the dash trim.



There are some small gaps in the corners and that bottom piece could be brought forward further as I can now see in direct sunlight. What appear to be scratches in the forward most part are actually reflections from some chrome bits on the unit. The scratch below the Voice button is real.