Test P - Introduction

NOTE: Perform this test when Code 18 or 49 is displayed during QUICK TEST or when directed here by other test procedures. This test is intended to diagnose the following:

Harness circuits (SPOUT, SAW)
Base timing
Faulty ECA
NOTE: To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault:
Basic engine condition (valves, vacuum leaks, valve timing, EGR valve, etc.)
Distributor
TFI, DIS or EDIS module
Camshaft sensor (CID)
Single Hall Crankshaft Sensor (PIP signal)
Dual Hall Sensor

Fig 1: TFI Applications Spark Timing Check Circuit

Fig 2: 2.3L OHC PFI Truck (DIS) IDM Circuit

Fig 3: 4.0L MA PFI Truck (EDIS) IDM Circuit