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OBD1 ECU Chipping Wirelist

Pin connections and traces between the MCU, latch, and external EPROM socket on OBD1 Honda ECUs.

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Adapted from pgmfi.org wiki

Use this archived Honda OBD1 ECU wirelist to diagnose continuity problems after installing an external ROM socket and 74HC373 latch. It records known connections between the latch, ROM socket, 66K MCU, IC9, resistor pack RM3, and nearby board components.

Caution

Disconnect the ECU from the vehicle before continuity testing. These mappings are archived community observations, not a substitute for a verified schematic for your exact board.

Continuity-testing procedure

  1. Inspect the 74HC373 latch and ROM socket for solder bridges.
  2. With a continuity tester, check every pair of adjacent pins around both packages. Adjacent pins should not have continuity.
  3. Put one probe where each package pin enters the component.
  4. Check that pin against at least one expected connection in the searchable wirelist below.
  5. Use listed feed-throughs (FT) to test continuity between an IC pin and the board where available.

Pin-numbering notes

  • DIP pins begin at pin 1 beside the notch or dot, run down the left side, and continue back up the right side.
  • RM3 is a single-inline-package resistor pack; its pin 1 is marked on the silkscreen.
  • On the JDM P30 board, 66K MCU pin 1 is in the middle of one side of the square surface-mount package. Several MCU pin numbers are marked on the board.
  • Signal names beginning with / are active low.

Searchable wirelist

Use the ECU-family and component filters, or search for a pin, signal, or connected component.

OBD1 ECU chipping connections

of 96 connections

JDM P30-901 373 latch
Test point Pin 1 /OE
  1. 373 Pin 10
  2. FT
  3. ROM Pin 14 GND
  4. ROM Pin 20 /CE
JDM P30-901 373 latch
Test point Pin 2 1Q
  1. RM3 Pin 5
  2. ROM Pin 10 A0
JDM P30-901 373 latch
Test point Pin 3 1D
  1. RM3 Pin 9
  2. ROM Pin 11 I/O0
  3. 66K Pin 2 AD0
  4. IC9 Pin 11
JDM P30-901 373 latch
Test point Pin 4 2D
  1. RM3 Pin 8
  2. ROM Pin 12 I/O1
  3. 66K Pin 3 AD1
  4. IC9 Pin 12
JDM P30-901 373 latch
Test point Pin 5 2Q
  1. ROM Pin 9 A1
JDM P30-901 373 latch
Test point Pin 6 3Q
  1. ROM Pin 8 A2
JDM P30-901 373 latch
Test point Pin 7 2D
  1. RM3 Pin 7
  2. ROM Pin 13 I/O2
  3. 66K Pin 4 AD2
  4. IC9 Pin 13
The archived latch list identifies this signal as 2D; the corresponding ROM list identifies it differently.
JDM P30-901 373 latch
Test point Pin 8 2D
  1. RM3 Pin 6
  2. ROM Pin 15 I/O3
  3. 66K Pin 5 AD3
  4. IC9 Pin 14
The archived latch list identifies this signal as 2D; the corresponding ROM list identifies it differently.
JDM P30-901 373 latch
Test point Pin 9 4Q
  1. ROM Pin 7
JDM P30-901 373 latch
Test point Pin 10 GND
  1. 373 Pin 1
  2. FT
  3. ROM Pin 14 GND
  4. ROM Pin 20 /CE
JDM P30-901 373 latch
Test point Pin 11 LE
  1. C91
  2. 66K Pin 24 ALE
JDM P30-901 373 latch
Test point Pin 12 5Q
  1. ROM Pin 4 A6
JDM P30-901 373 latch
Test point Pin 13 5D
  1. ROM Pin 18 I/O6
  2. 66K Pin 8 AD6
  3. IC9 Pin 17
JDM P30-901 373 latch
Test point Pin 14 6D
  1. ROM Pin 19 I/O7
  2. 66K Pin 9 AD7
  3. IC9 Pin 18
JDM P30-901 373 latch
Test point Pin 15 6Q
  1. FT
  2. ROM Pin 3 A7
JDM P30-901 373 latch
Test point Pin 16 7Q
  1. FT
  2. ROM Pin 5 A5
JDM P30-901 373 latch
Test point Pin 17 7D
  1. ROM Pin 17 I/O5
  2. 66K Pin 7 AD5
  3. IC9 Pin 16
JDM P30-901 373 latch
Test point Pin 18 8D
  1. ROM Pin 16 I/O4
  2. 66K Pin 6 AD4
  3. IC9 Pin 15
JDM P30-901 373 latch
Test point Pin 19 8Q
  1. ROM Pin 6 A4
JDM P30-901 373 latch
Test point Pin 20 VCC
  1. C49
  2. ROM Pin 28 VCC
  3. ROM Pin 1 /WE
JDM P30-901 ROM socket
Test point Pin 1 VCC
  1. ROM Pin 28 VCC
  2. C49
  3. 373 Pin 20 VCC
JDM P30-901 ROM socket
Test point Pin 2 A12
  1. 66K Pin 14 A12
JDM P30-901 ROM socket
Test point Pin 3 A7
  1. FT
  2. 373 Pin 15 6Q
JDM P30-901 ROM socket
Test point Pin 4 A6
  1. FT
  2. 373 Pin 12 5Q
JDM P30-901 ROM socket
Test point Pin 5 A5
  1. FT
  2. 373 Pin 16 7Q
JDM P30-901 ROM socket
Test point Pin 6 A4
  1. 373 Pin 19 8Q
JDM P30-901 ROM socket
Test point Pin 7 A3
  1. 373 Pin 9 4Q
JDM P30-901 ROM socket
Test point Pin 8 A2
  1. FT
  2. 373 Pin 6 3Q
JDM P30-901 ROM socket
Test point Pin 9 A1
  1. FT
  2. 373 Pin 5 2Q
JDM P30-901 ROM socket
Test point Pin 10 A0
  1. RM3 Pin 5
  2. FT
  3. 373 Pin 2 1Q
JDM P30-901 ROM socket
Test point Pin 11 I/O0
  1. RM3 Pin 9
  2. 373 Pin 3 1D
  3. 66K Pin 2 AD0
  4. IC9 Pin 11
JDM P30-901 ROM socket
Test point Pin 12 I/O1
  1. RM3 Pin 8
  2. 373 Pin 4 2D
  3. 66K Pin 3 AD1
  4. IC9 Pin 12
JDM P30-901 ROM socket
Test point Pin 13 I/O2
  1. RM3 Pin 7
  2. 373 Pin 7 3D
  3. 66K Pin 4 AD2
  4. IC9 Pin 13
JDM P30-901 ROM socket
Test point Pin 14 GND
  1. ROM Pin 20 /CE
  2. FT
  3. 373 Pin 10 GND
  4. FT
  5. 373 Pin 1 /OE
JDM P30-901 ROM socket
Test point Pin 15 I/O3
  1. RM3 Pin 6
  2. 373 Pin 8 4D
  3. 66K Pin 5 AD3
  4. IC9 Pin 14
JDM P30-901 ROM socket
Test point Pin 16 I/O4
  1. 373 Pin 18 8D
  2. 66K Pin 6 AD4
  3. IC9 Pin 15
JDM P30-901 ROM socket
Test point Pin 17 I/O5
  1. 373 Pin 17 7D
  2. 66K Pin 7 AD5
  3. IC9 Pin 16
JDM P30-901 ROM socket
Test point Pin 18 I/O6
  1. 373 Pin 13 5D
  2. 66K Pin 8 AD6
  3. IC9 Pin 17
JDM P30-901 ROM socket
Test point Pin 19 I/O7
  1. 373 Pin 14 6D
  2. 66K Pin 9 AD7
  3. IC9 Pin 18
JDM P30-901 ROM socket
Test point Pin 20 /CE
  1. ROM Pin 14 GND
  2. FT
  3. 373 Pin 10 GND
  4. FT
  5. 373 Pin 1 /OE
JDM P30-901 ROM socket
Test point Pin 21 A10
  1. FT
  2. 66K Pin 12 A10
JDM P30-901 ROM socket
Test point Pin 22 /OE
  1. C29
  2. R39 on the back of the board
  3. 66K Pin 25 /PSEN
JDM P30-901 ROM socket
Test point Pin 23 A11
  1. FT
  2. 66K Pin 13 A11
JDM P30-901 ROM socket
Test point Pin 24 A9
  1. FT
  2. 66K Pin 11 A9
JDM P30-901 ROM socket
Test point Pin 25 A8
  1. FT
  2. 66K Pin 10 A8
JDM P30-901 ROM socket
Test point Pin 26 A13
  1. 66K Pin 15 A13
JDM P30-901 ROM socket
Test point Pin 27 A14
  1. 66K Pin 16 A14
JDM P30-901 ROM socket
Test point Pin 28 VCC
  1. ROM Pin 1 /WE
  2. C49
  3. 373 Pin 20 VCC
USDM P28 / P05 373 latch
Test point Pin 1 /OE
  1. 373 Pin 10
  2. ROM Pin 14 GND
USDM P28 / P05 373 latch
Test point Pin 2 1Q
  1. ROM Pin 10 A0
USDM P28 / P05 373 latch
Test point Pin 3 1D
  1. RM3 Pin 2
  2. ROM Pin 11 I/O0
  3. 66K Pin 1 AD0
USDM P28 / P05 373 latch
Test point Pin 4 2D
  1. RM3 Pin 3
  2. ROM Pin 12 I/O1
  3. 66K Pin 2 AD1
USDM P28 / P05 373 latch
Test point Pin 5 2Q
  1. ROM Pin 9 A1
USDM P28 / P05 373 latch
Test point Pin 6 3Q
  1. ROM Pin 8 A2
USDM P28 / P05 373 latch
Test point Pin 7 2D
  1. RM3 Pin 4
  2. ROM Pin 13 I/O2
  3. 66K Pin 3 AD2
USDM P28 / P05 373 latch
Test point Pin 8 2D
  1. RM3 Pin 5
  2. ROM Pin 15 I/O3
  3. 66K Pin 4 AD3
USDM P28 / P05 373 latch
Test point Pin 9 4Q
  1. ROM Pin 7
USDM P28 / P05 373 latch
Test point Pin 10 GND
  1. 373 Pin 1
  2. ROM Pin 14 GND
USDM P28 / P05 373 latch
Test point Pin 11 LE
  1. 66K Pin 22 ALE
USDM P28 / P05 373 latch
Test point Pin 12 5Q
  1. ROM Pin 4 A6
USDM P28 / P05 373 latch
Test point Pin 13 5D
  1. RM3 Pin 8
  2. ROM Pin 18 I/O6
  3. 66K Pin 7 AD6
USDM P28 / P05 373 latch
Test point Pin 14 6D
  1. RM3 Pin 9
  2. ROM Pin 19 I/O7
  3. 66K Pin 8 AD7
USDM P28 / P05 373 latch
Test point Pin 15 6Q
  1. ROM Pin 3 A7
USDM P28 / P05 373 latch
Test point Pin 16 7Q
  1. ROM Pin 5 A5
USDM P28 / P05 373 latch
Test point Pin 17 7D
  1. RM3 Pin 7
  2. ROM Pin 17 I/O5
  3. 66K Pin 6 AD5
USDM P28 / P05 373 latch
Test point Pin 18 8D
  1. RM3 Pin 6
  2. ROM Pin 16 I/O4
  3. 66K Pin 5 AD4
USDM P28 / P05 373 latch
Test point Pin 19 8Q
  1. ROM Pin 6 A4
USDM P28 / P05 373 latch
Test point Pin 20 VCC
  1. ROM Pin 28 VCC
  2. ROM Pin 1 /WE
USDM P28 / P05 ROM socket
Test point Pin 1 VCC
  1. ROM Pin 28 VCC
  2. 373 Pin 20 VCC
USDM P28 / P05 ROM socket
Test point Pin 2 A12
  1. 66K Pin 13 A12
USDM P28 / P05 ROM socket
Test point Pin 3 A7
  1. 373 Pin 15 6Q
USDM P28 / P05 ROM socket
Test point Pin 4 A6
  1. 373 Pin 12 5Q
USDM P28 / P05 ROM socket
Test point Pin 5 A5
  1. 373 Pin 16 7Q
USDM P28 / P05 ROM socket
Test point Pin 6 A4
  1. 373 Pin 19 8Q
USDM P28 / P05 ROM socket
Test point Pin 7 A3
  1. 373 Pin 9 4Q
USDM P28 / P05 ROM socket
Test point Pin 8 A2
  1. 373 Pin 6 3Q
USDM P28 / P05 ROM socket
Test point Pin 9 A1
  1. 373 Pin 5 2Q
USDM P28 / P05 ROM socket
Test point Pin 10 A0
  1. 373 Pin 2 1Q
USDM P28 / P05 ROM socket
Test point Pin 11 I/O0
  1. RM3 Pin 2
  2. 373 Pin 3 1D
  3. 66K Pin 1 AD0
USDM P28 / P05 ROM socket
Test point Pin 12 I/O1
  1. RM3 Pin 3
  2. 373 Pin 4 2D
  3. 66K Pin 2 AD1
USDM P28 / P05 ROM socket
Test point Pin 13 I/O2
  1. RM3 Pin 4
  2. 373 Pin 7 3D
  3. 66K Pin 3 AD2
USDM P28 / P05 ROM socket
Test point Pin 14 GND
  1. 373 Pin 10 GND
  2. 373 Pin 1 /OE
USDM P28 / P05 ROM socket
Test point Pin 15 I/O3
  1. RM3 Pin 5
  2. 373 Pin 8 4D
  3. 66K Pin 4 AD3
USDM P28 / P05 ROM socket
Test point Pin 16 I/O4
  1. RM3 Pin 6
  2. 373 Pin 18 8D
  3. 66K Pin 5 AD4
USDM P28 / P05 ROM socket
Test point Pin 17 I/O5
  1. RM3 Pin 7
  2. 373 Pin 17 7D
  3. 66K Pin 6 AD5
USDM P28 / P05 ROM socket
Test point Pin 18 I/O6
  1. RM3 Pin 8
  2. 373 Pin 13 5D
  3. 66K Pin 7 AD6
USDM P28 / P05 ROM socket
Test point Pin 19 I/O7
  1. RM3 Pin 9
  2. 373 Pin 14 6D
  3. 66K Pin 8 AD7
USDM P28 / P05 ROM socket
Test point Pin 20 /CE
  1. R54 and the other side of R54 is connected to GND
USDM P28 / P05 ROM socket
Test point Pin 21 A10
  1. 66K Pin 11 A10
USDM P28 / P05 ROM socket
Test point Pin 22 /OE
  1. R49
  2. 66K Pin 23 /PSEN
USDM P28 / P05 ROM socket
Test point Pin 23 A11
  1. 66K Pin 12 A11
USDM P28 / P05 ROM socket
Test point Pin 24 A9
  1. 66K Pin 10 A9
USDM P28 / P05 ROM socket
Test point Pin 25 A8
  1. 66K Pin 9 A8
USDM P28 / P05 ROM socket
Test point Pin 26 A13
  1. 66K Pin 14 A13
USDM P28 / P05 ROM socket
Test point Pin 27 A14
  1. 66K Pin 15 A14
USDM P28 / P05 ROM socket
Test point Pin 28 VCC
  1. ROM Pin 1 /WE
  2. 373 Pin 20 VCC

No matching connections.

Source notes and uncertainties

Important

The JDM P30-901 latch list labels latch pins 7 and 8 as 2D, while the corresponding ROM-socket list labels those connections as 3D and 4D. The searchable data preserves the archived labels and flags the contradiction instead of silently correcting it.

  • The JDM P30-901 list was recorded on December 28, 2004.
  • The USDM P28/P05 list was recorded on November 14, 2005.
  • The source says the P05 mapping was validated later and that the ROM pin 20 resistor name was corrected to R54.
  • Compatibility beyond the named ECUs was not confirmed in the archived source.

Related

Credits and source

Source Adapted from Ecu Chipping Wirelist on pgmfi.org wiki. Licensed under CC BY-NC-SA 1.0.