QuestionQUESTION: The gas gauge and temperature all of a sudden went to max and the tach is oscillating but the motor is idling steady. What could be the possible cause.
ANSWER: Hi there, I'm sorry for the late answer, I was very busy at work. The possible cause it could be bad grounding, faulty instrument cluster panel, or even the gauges. Disconnect the temperature gauge plug, (make sure it is not the coolant temp sensor.) Observe the temp gauge. If it still stays on the max reading then the gauge had failed. Same with the fuel gauge. If it moves then the sending unit had failed on both. Check all grounds and make sure that the body and the motor are grounded. Check for reference voltage at the fuel pump/float/sending unit. It is possible that the on board computer fails to ground the instruments or fails to receive a signal from them. Now the tach. Connect an external tach meter, (automotive multimeter with tach and dwell settings) and observe the rpm. You probably don't have one of those, but if the is an Auto Zone parts store in your area, they can connect a scanning tool and extract any trouble codes and motor behavior, like RPMs for example, for free. Then, take it from there.
Hope this helped. If you run the tests let me know what you find.
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QUESTION: Something I did not initially notice is the odometer is reading all 9's and the speedometer is not working. The trip odometers are incrementing but are not the same readings, differ by 100 plus kilometers when the fault is not there. Yesterday morning I started the truck and everything went back to morning. On the return trip later that day things returned back to the fault conditions. I have tried to run a temporary ground from the battery to the frame of the truck and nothing seems to of changed. I have also noticed recently that when the truck is idling that the headlights are pulsating. I am wondering is there is something in common between the two. Could just the ground to the instrument cluster be missing.... any suggestions on how to ground it to verify! Any help will be greatly appreciated... Thanks
ANSWER: Have you checked for trouble codes to rule out problem with the VSS? Also is your instrumentation digital or analog?
Thanks.
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QUESTION: I have check the codes using a code reader and the only code which comes up is P1105 which should be the map/baro switch. I disconnect the battery and noticed that the gas gauge still read maxim clockwise rotation. It seems it has gone beyond the full mark. The instruments are analog gauges with the odometer being digital. I also noticed that although the odometer is incrementing it is not the correct mileage.
AnswerFailure of analog instruments is not unusual. However, diagnosis of intermittent problems is a bit difficult. I would not say that you will need to replace anything right now, but usually the gas tank sending unit fails before the gauge does. On digital odometers, it is not only the display that fails but it can be the electronic circuit of the component or the Vehicle Speed Sensor. As for the MAP sensor, make sure that the vacuum line is connected and not leaky and the electrical connection on it is okay. On the reference voltage of the sensor connect a digital multimeter without disconnecting it from the circuit, using a hatpin or a paper clip and apply vacuum to the sensor's vacuum nipple with a hand pump. As the vacuum increases the voltage decreases which means that the sensor is working properly. But I would recommend to take the vehicle to a technician and let them spend an hour or so on it because like I said, intermittent problems are hard to diagnose especially with no "hands on" testing. In other words, it would have been much easier for me to come to a conclusion if I had this vehicle here and see exactly what it does. Hope this helps.
