This is the genuine Continental flex fuel sensor, GM part number 13577429 (Continental catalogue SE1004S) — the ethanol content sensor that standalone ECU manufacturers calibrate against. Plumbed into the fuel line, it continuously measures the true ethanol percentage and fuel temperature of the fuel actually in your system, so the ECU can blend ignition timing, injection and boost targets between petrol and E85 maps in real time. Pump “E85” is rarely 85% ethanol — winter blends drop to E70 or lower — and this sensor removes the guesswork that kills tuned engines.
Genuine Continental — not a copy. The body is printed “Continental” with raised moulded sections. Smooth, unbranded sensors sold cheaply online are counterfeits and are known to read 20–30% ethanol in plain petrol and jump erratically under load — dangerous errors when your timing map trusts the reading.
How the Signal Works
The sensor outputs a 12 V square wave on a single wire. Frequency carries ethanol content, pulse width carries fuel temperature:
| Signal | Meaning |
|---|---|
| 50 Hz | 0% ethanol (E0) |
| 150 Hz | 100% ethanol (E100) — linear: ethanol % = frequency − 50 |
| Pulse width 1 ms | Fuel temperature −40 °C |
| Pulse width 5 ms | Fuel temperature +125 °C |
| 180–190 Hz | Contaminated fuel (water or methanol detected) |
| Below 50 Hz | Wiring fault / short — check ground and pull-up |
Connector pinout: Pin A — battery 12 V, Pin B — ground (signal ground, not chassis 0 V), Pin C — signal output (open-collector; use the ECU’s internal pull-up on a digital input).
Technical Specifications
| Property | Value |
|---|---|
| Part number | GM 13577429 (Continental SE1004S) |
| Manufacturer | Continental (genuine, made in Mexico) |
| Ethanol range | 0–100%, ±5% accuracy |
| Fuel temperature range | −40 °C to +125 °C |
| Ambient temperature rating | −40 °C to +150 °C |
| Max fuel pressure | 13.5 bar (189 psi) |
| Max flow | 400 l/h — no meaningful restriction |
| Ports | 3/8″ (10 mm) GM quick-connect, inlet and outlet |
| Supply voltage | 12 V DC |
| Output | Digital square wave — frequency + pulse width |
| Connector | GM/Delphi GT150 3-pin sealed |
| Body | Compact “short” version, no mounting tabs |
GM Flex Fuel Sensor Versions
| Part number | Body | Mounting | Temp rating |
|---|---|---|---|
| 13577429 (this sensor) | Smallest, short ports | No tabs — supported by the fuel line | +150 °C ambient |
| 13577379 | Mid-size | 3 mounting holes | +125 °C |
| 13577394 | Large, longer port pipes | 3 mounting holes | +125 °C |
All three share identical electronics and the same 50–150 Hz calibration, so any ECU flex fuel preset works with this sensor. The 13577429 is the pick for tight engine bays and highest under-bonnet temperatures.
ECU Integration
Wire the signal to a digital/frequency input and enable the built-in flex fuel function:
| ECU | Input configuration |
|---|---|
| Link ECU (G4X/G5) | Any DI — Fuel Composition function |
| Emtron (KV/SL) | Digital input — Fuel Composition |
| MoTeC M1 | UDig hybrid input — set fuel calibration to “Ethanol”, not “E85” (E85 caps the scale) |
| Haltech Elite/Nexus | SPI input — falling edge, pull-up enabled |
| ECUMaster EMU Black | Dedicated Flex Fuel input |
| MaxxECU / AEM | Digital input — flex fuel function |
Installation
- Install in-line with the fuel system — commonly in the return line after the pressure regulator (low pressure, zero restriction concern), or in the feed line before the rail where faster blend response is wanted. Rated to 13.5 bar either way.
- The ports are GM 3/8″ quick-connect. For braided-hose systems use the Quick Connector AN6 for 3/8″ Pipe or Quick Connector AN8 for 3/8″ Pipe adapters.
- Keep the sensor full of fuel — trapped air skews readings. The sensor only outputs a reading while fuel is flowing through it.
- Wiring: use the Ethanol Content Connector KIT GM Type — the mating GT150 3-way sealed connector with terminals.
Frequently Asked Questions
How do I know this is a genuine Continental sensor and not a counterfeit?
Genuine sensors carry the moulded “Continental” name and raised square sections on the body, and read ~0% in pure petrol. Counterfeits are smooth-bodied, often with ground-off part numbers, and give erratic readings (20–30% ethanol in straight petrol). XTRA Motorsport supplies the genuine Continental unit only.
Do I need a separate connector for it?
Yes — the sensor uses a GM/Delphi GT150 3-pin sealed connector that is not included with the bare sensor. The matching connector kit with terminals is available: Ethanol Content Connector KIT GM Type.
Feed line or return line?
Both work within the 13.5 bar rating. The return line after the regulator is the classic low-pressure location with zero flow-restriction concern; the feed line before the rail responds slightly faster to a fresh tank of different blend. In returnless systems, use the feed line.
Can it read E100, and is there an ECU calibration catch?
Yes — the scale is linear from 50 Hz (E0) to 150 Hz (E100). On MoTeC M1, set the fuel calibration to “Ethanol” rather than “E85”, otherwise the blend axis is capped at E85.
Does it work with methanol?
No. It is designed for ethanol/petrol blends only — methanol reads as contamination (output above 150 Hz) and its chemistry can damage the sensor.
What does a reading above 150 Hz mean?
Fuel contamination — typically water (around 180 Hz) or methanol. The sensor has built-in self-diagnostics; below 50 Hz indicates a wiring fault or short.
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