Test H - Introduction

NOTE: For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article.

NOTE: Perform this test when Code 41, 91, 42, 92, 43, 65, 85, 86 or 93 is displayed during QUICK TEST or when directed here by other test procedures.

NOTE: See General Pinpoint Test Notes at beginning of pinpoint tests before performing this test. Fuel contaminated engine oil may affect Codes 41, 91, 42, or 92. If this is suspected, remove PCV valve from valve cover and repeat QUICK TEST. If problem is corrected, change engine oil and filter.

NOTE: Use this test to diagnose only the following components:

HEGO sensor
HEGO signal and ground circuit
HEGO sensor connection
Vacuum systems
Fuel injector
ECA
Electrical circuits (HEGO GND, HEGO, INJ 1-8, VPWR and SIG RTN)
NOTE: To prevent replacement of good components, be aware of the following non-EEC areas which may be the cause of driveability concerns:
Ignition coil, distributor cap or rotor
Faulty or fouled spark plugs or wires
Faulty CANP system
Distributorless Ignition System (DIS)
EGR valve and gasket
Air filter
Fuel or engine oil contamination
Poor electrical ground
Faulty fuel pressure
Intake or exhaust system leaks
Engine below normal operating temperature

TRUCK - INDIVIDUAL INJECTOR RESISTANCE ⁽¹⁾

Engine

Ohms

2.3L

15.0-18.0

All Others

13.0-16.0

⁽¹⁾	Resistance values are for a single injector.

TRUCK INJECTOR BANK RESISTANCE

Engine	Ohms
2.3L PFI	7.0-9.5
2.9L & 4.9L PFI	5.0-6.5
5.0L, 5.8L & 7.5L PFI	3.0-4.0

TEST PIN WIRE COLOR IDENTIFICATION

Application		Wire Color
Pin 29 (Right HEGO)		Tan/Orange
Pin 43 (Left HEGO)		Tan/Red
Pin 58
2.3L & 2.9L		Light Green/White
All Others		Tan/Orange
Test Pin No. 59		Tan/Red

Fig 1: 5.0L & 5.0L MA PFI Test Schematic

Fig 2: 2.3L MA, 2.9L MA, 4.0L, 4.9L & 5.8L PFI (Truck) Schematic

Fig 3: Test Schematic For All Other PFI Engines

NOTE: KOER Codes 41 and 91 are HEGO codes that indicate the system is always lean. KOER Codes 42 and 92 indicate the system is always rich. For vehicles equipped with dual HEGO's Codes 41 and 42 refer to Right (rear) HEGO sensors. Codes 91 and 92 refer to Left (front) HEGO sensors.