LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Porsche >> 1985 >> 928 Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Fuel Injection System - BOSCH LH >> Testing >> Test 11 >> Power Supply For LH Control Unit & Fuel Pump
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Power Supply For LH Control Unit & Fuel Pump

  1. Connect voltmeter on terminals 9 and 5 of disconnected LH control unit plug. Turn ignition switch to the "ON" position. Connect W21 (CEB) to ground with a jumper wire.
  2. If battery voltage is not shown, connect voltmeter on connected plug W23 (CEB) and ground. If battery voltage is still not shown, remove jumper wire W21 (CEB). Bridge terminals 30 and 87 on socket of relay XXV (LH-Jetronic). Battery voltage shown will be at connected plug W23 (CEB) and ground. If no is voltage is shown, check relay and activation.
  3. Check control signals from EZF control unit to LH control unit. With EXF control unit plug connected, pull off LH control unit plug. Connect tester on terminal 1 of LH control unit plug using manufacturer's instructions. Operate starter. Oscilloscope should display control signal.
  4. If control signal is not displayed, check continuity from terminal 1 (LH control unit plug) to terminal 16 (EZF control unit plug). If continuity is okay, replace EZF control unit.
scientia non olet · About LEMON Manuals