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MegaSquirt DB37 Connector & DB9 Serial Schematic with U6 Voltage Test Points

Megasquirt connector schematic with DB9, MAX232, DB37 P2 connector and signal jumpers
Megasquirt connector schematic with DB9, MAX232, DB37 P2 connector and signal jumpersOriginal file
Megasquirt connector schematic with DB9, MAX232, DB37 P2 connector and signal jumpers

Reference · 1993-1997 ProbeAll 25 schematics

MegaSquirt II Power Supply & CPU Clock Schematic with Voltage Test Readings MegaSquirt DB37 & DB9 Connector Schematic - Pinout, Jumpers & Test Voltages Megasquirt MSII Power Supply Schematic - LM2937ET-5.0 5V Regulator & CPU Clock MegaSquirt DB37 Connector & DB9 Serial Schematic with U6 Voltage Test Points Ford Probe ECT/CLT Sensor Circuit Mod Schematic - Before/After Comparator Sketch Ford Probe Cooling Fan Relay Comparator Mod Schematic - Denso 179700-0220 ECT Ford Probe DIY High-Speed Fan Trigger Circuit - LM393 Comparator Schematic 60-2 Crank Trigger Wheel Diagram - Tooth Positions A/B/C, VR Sensor Alignment Exhaust Venturi Turbo Flow Schematic - Intake Air, Fuel & Exhaust Gas Diagram Twincharged Setup Schematic - M62 Supercharger + T66 Turbo Plumbing Diagram 25schematics1993-1997 Ford Probe More reference 2000 Mazda 626 2.5L Engine Performance Wiring Diagram - PCM Pins & O2 SensorsWiring diagram 3-Position Rotary Selector Switch: Contact Positions #1 & #2 DiagramBrochure Ford 2012 MY vehicle emission control information label for a 5.0L gasoline engineSpec plate 1993 Ford Probe Two Speed Cooling Fan Circuit Operation - 2.0L & 2.5LService procedure 1993 Ford Probe Compound Turbo & Intercooler Plumbing Routing DiagramVacuum routing 1993-94 Ford Probe Engine Bay Component Location Diagram - Relays, Fans, GroundsExploded parts Manual transaxle specifications screen with lubricant grade, 2.0L and 2.5L gear ratios and differential shim sManual page Hub Spacer Ring Blueprint - Ø77.75 OD x Ø72.00 ID x 6.35 Thick (Ford Probe)Blueprint Connecting Rod Bolt Torque Specs & Clearances - 8740 Cap Screw Instruction SheetTorque spec

Megasquirt ECU connector schematic showing the DB9 serial interface, MAX232, input signal jumpers and the DB37 main connector pinout.

Part of 1993-1997 Ford Probe Schematics

AI caption · Photo 232 of 676

This document is a page from a MegaSquirt DIY engine management (EFI controller) schematic, specifically the "Megasquirt - Connector" sheet. It shows the serial communications circuit built around U6 (a 16-pin RS-232 level converter with C1+/C1-/C2+/C2- charge-pump capacitors C26-C29, all 0.1 µF) connecting TXD-1 and RXD-1 to a DB9 connector (P1), with CTS and RTS jumper positions. Handwritten red voltage measurements have been added at various points on the charge-pump circuit (4.96v, 8.8v, 6.8v, 2.4v, 4.5v, -4.32v, -8.37v, 0v, 5v), suggesting the sheet was used to diagnose a serial communications or U6 chip fault. The lower half shows the main DB37 connector (P2) with its 37 numbered pins and the signals routed to it: MAT, CLT, TPS, O2, TachIn, 12 RAW, IDL, INJ-1, INJ-2, FP1, plus IAC1A/IAC1B/IAC2A/IAC2B and IGN jumpers, four spare signal jumpers (SPR1-SPR4), Vref, and polyfuse F2 (RXE050). A partial note explains that for MS-II certain CPU-to-connector signal jumpers are used: JS0-IAC1A, JS1-IAC1B, JS2-IAC2A, JS3-IAC2B, JS10-IGN. Useful for troubleshooting MegaSquirt serial comms and DB37 wiring.

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Frequently asked questions

What jumper settings does the note list for MS-II?
The note lists CPU-to-connector jumpers: JS0 - IAC1A, JS1 - IAC1B, JS2 - IAC2A, JS3 - IAC2B, and JS10 - IGN.
What signals go to the DB37 connector (P2) on this schematic?
MAT, CLT, TPS, O2, TachIn, 12 RAW, IDL, INJ-1, INJ-2, FP1, plus IAC1A/IAC1B/IAC2A/IAC2B and IGN jumper outputs, Vref through polyfuse F2, and spare signals SPR1-SPR4.
What are the capacitor values around U6?
C26, C27, C28, and C29 are all 0.1 (µF) charge-pump/decoupling capacitors around the U6 serial level-converter IC.
What voltages were measured on the U6 serial circuit?
Handwritten measurements show 4.96v at C26, 8.8v and 6.8v on the V+ side, 2.4v and 4.5v at the C2 pins, -4.32v and -8.37v on the V- side, 0v at C29, 5v at VCC, and 0v at the DB9 connector.
What fuse protects the Vref line?
F2, a Polyfuse RXE050, is in series with the Vref line.

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