System Tests: Notes

WARNING: Deactivate air bag system before performing any service operation involving instrument panel or steering column components. See appropriate AIR BAG RESTRAINT SYSTEMS article. Do not apply electrical power to any component on instrument panel or steering column without first deactivating air bag system. Air bag may deploy.

CAUTION: When battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION before disconnecting battery.

CAUTION: Turn ignition switch to LOCK position and disconnect battery before disconnecting Generic Electronic Module (GEM) harness connectors. Failure to do so will result in GEM storing erroneous codes and may also result in erratic operation of GEM after reconnecting battery.

CAUTION: Use correct probe adapter when taking measurements. Failure to use proper adapter may cause damage to harness connector.

NOTE: Before beginning system tests, perform PRELIMINARY INSPECTION under TROUBLE SHOOTING. A Digital Volt-Ohmmeter (DVOM) is required to test the analog instrument panel system. After repairs are complete, ensure all components are correctly installed and all harness connectors are connected correctly.

NOTE: SYSTEM TESTS do not include Motorhomes. After making any repair, clear codes and perform data link diagnostic test. See DATA LINK DIAGNOSTIC TEST under SELF-DIAGNOSTIC SYSTEM in MODULE COMMUNICATIONS NETWORK - EXCURSION & F250-F550 SUPER DUTY PICKUPS article.

NOTE: Generic Electronic Module (GEM) may also be referred to as Central Timer Module (CTM).

SYMPTOM INDEX

Symptom

Perform System Test

No Scan Tool Communication With Generic Electronic Module ⁽¹⁾

All Gauges Inoperative

Fuel Gauge Reads Incorrectly

Low Fuel Warning Indicator Never On

Low Fuel Indicator Always On

⁽²⁾

Voltage Gauge Reads Incorrectly

Oil Pressure Gauge Reads Incorrectly

Engine Temperature Gauge Reads Incorrectly

Speedometer Inoperative

Trip Odometer Inoperative, Speedometer Okay

⁽³⁾

Tachometer Reads Incorrectly

Speedometer Reads Incorrectly, Odometer Okay

Yellow Brake (ABS) Warning Indicator Always/Never On

Red Brake Warning Indicator Always/Never On

SERVICE ENGINE SOON Warning Indicator Inoperative

SERVICE ENGINE SOON Warning Indicator Always On

⁽⁴⁾

Charge System Warning Indicator Inoperative

Charge System Warning Indicator Always On

⁽⁵⁾

Air Bag Warning Indicator Always/Never On

High Beam Indicator Inoperative

Left Turn Signal Indicator Inoperative

Right Turn Signal Indicator Inoperative

DOOR AJAR Warning Indicator Inoperative, Chime Operative

Safety Belt Warning Indicator Inoperative Or Does Not Operate Correctly, Chime Operative Or Does Not Operate Correctly

4X4/4X4 LOW RANGE Indicator Inoperative (Manual Shift)

4X4/4X4 LOW RANGE Indicator Always On (Manual Shift)

4X4/4X4 LOW RANGE Indicator Inoperative (Automatic)

⁽⁶⁾

WAIT TO START Warning Indicator Inoperative (Diesel)

WATER IN FUEL Warning Indicator Inoperative (Diesel)

Speed Control Indicator Is Always/Never On

Theft Indicator Is Always/Never On (Excursion)

No Communication With Compuvalve (Bi-Fuel Only)

Incorrect Fuel Gauge Reading In Alternative Fuel Mode (Bi-Fuel Only)

Incorrect Fuel Gauge Reading In Gasoline Mode (Bi-Fuel Only)

Incorrect Fuel Gauge Indication in Alternative Fuel Mode & Gasoline Mode (Bi-Fuel Only)

Instrument Cluster Inoperative (Bi-Fuel Only)

⁽¹⁾	Generic Electronic Module (GEM) may also be referred to as Central Timer Module (CTM).

⁽²⁾	Replace instrument cluster. See REMOVAL & INSTALLATION .

⁽³⁾	Verify trip odometer reset lever is not binding. If okay, replace instrument cluster. See REMOVAL & INSTALLATION .

⁽⁴⁾	See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.

⁽⁵⁾	See appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS.

⁽⁶⁾	See appropriate ELECTRONIC CONTROLS article in AUTOMATIC TRANSMISSIONS.