AEM Wideband Series-X OBD1

OBD1 P28 Wideband Wiring & Hondata S300 Setup Guide

Complete Wideband Installation Guide for OBD1 P28 & Hondata S300

AEM 30-0300, 30-4100 & All 0–5V Analog AEM Widebands

This guide covers proper installation, wiring, and Hondata S300 configuration for AEM wideband controllers on OBD1 P28-style ECUs.

Primary configuration covered:

  • ECU: P28 OBD1
  • Software: Hondata S300 v3 (emulator compatible)
  • Analog Input: D14 (Primary O2 Input)
  • Wideband Type: AEM 30-0300, 30-4100, and all 0–5V analog AEM outputs
  • Stock narrowband replaced or bypassed

This is a full technical breakdown — wiring, grounding, calibration, and setup.

Running a P28 OBD1 build? The VTI StreetSpec OBD1 Engine Harness is pre-configured for P28 ECU integration with clean sensor routing and auxiliary wires ready for wideband installs.

Understanding Wideband vs Narrowband

A narrowband O2 sensor only reports rich or lean in a binary fashion — it cannot provide accurate AFR data across the full operating range. A wideband controller measures actual lambda/AFR values continuously, which is essential for tuning on Hondata S300.

Wiring the AEM Wideband to OBD1 P28

The AEM wideband analog output (0–5V) connects to the ECU’s D14 pin — the primary O2 sensor input on the P28. This replaces the stock narrowband signal.

Key wiring points:

  • AEM analog output → ECU D14 (O2 signal input)
  • AEM ground → ECU sensor ground (not chassis ground)
  • AEM 12V → Switched ignition source (fused)
  • Sensor heater power → Switched 12V (separate fused circuit recommended)

Do not share the wideband ground with chassis or body ground points. Signal contamination from a shared ground is a common source of erratic AFR readings.

Hondata S300 Configuration

In SManager, set the O2 sensor type to wideband and configure the input scaling to match the AEM 0–5V output curve. The AEM 30-0300 and 30-4100 use the same analog output scaling.

Steps:

  1. Parameters → O2 Sensor → Set to Wideband
  2. Set input voltage range: 0–5V
  3. Set AFR scaling to match AEM output table (7.35–22.39 AFR)
  4. Verify live AFR reading at idle before tuning

Common Wideband Wiring Issues

Erratic AFR readings: Usually a grounding issue. Verify sensor ground goes directly to ECU sensor ground, not chassis.

Flat 14.7 reading: Stock narrowband still in circuit or D14 not properly connected to wideband output.

No reading in S300: Check O2 sensor type setting in SManager and verify analog output voltage at D14 with a multimeter.

Shop Products Referenced in This Guide

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