Blank Fuel Data Display

Fig. 33 Fuel data wiring circuit:

1. The ECM determines fuel consumption based on vehicle speed and fuel delivered to the engine. This information is sent to the ECC control head through circuit 461. The ECC control head interprets this information and illuminates the appropriate segments of the ``Fuel Data'' display panel.
2. If the ECC control head does not function properly, check blower operation in ``Defrost'' mode. If the blower does not operate, the air conditioning system is at fault. Repair as necessary.
3. If the ECC control-head operates properly or the blower works in ``Defrost,'' but ``Fuel Data'' panel is still blank, check circuit 155 for an open and repair as necessary. If circuit is satisfactory, connect voltmeter between control head pin 3 and ground.
4. If voltage fluctuates between 2 and 4 volts, enter the diagnostic mode. If ``(-) 1.8.8'' is displayed, replace data panel. If ``(-) 1.8.8'' is not displayed, replace control head.
5. If voltage does not fluctuate, disconnect ECC control head connector and connect voltmeter between pin 3 of harness connector and ground. If voltage now fluctuates, replace control head. If voltage does not fluctuate, check circuit 461, Figs. 33, for an open or short circuit and repair as necessary. If circuit is satisfactory, fault is in ECM connector or PROM installation, or in the ECM or PROM itself. Repair or replace as necessary.