C4 Sensor Information

The C4 Corvette makes use of numerous sensors that feed information to the ECM/PCM (Electronic Control Module/Powertrain Control Module) and to the instruments on the dashboard. Even if the sensor is operated by vacuum or pressure, the output is converted into an electrical signal for processing by the ECM. Most faulty sensors will cause a trouble code to be set (resulting in a 'Check Engine/SYS ' Light) and also alter the performance of the automobile.

When troubleshooting the reason for the code, the normal approach is to go straight to the sensor and assume that it is faulty. While this may be the normal practice, you are strongly cautioned that it is seldom the sensor but rather a connector, a power problem or a grounding issue that is actually causing the problem. Or, the sensor may simply be doing it's job and reporting an occurrence that is at variance with what is allowed or expected by the ECM/PCM.

In any event, because the sensor really is the easiest thing to check, the following information is provided to assist you in determining if the device is operating properly. You will need a D-VOM (Digital Volt-Ohm Meter) to check the items below. It should have at least a 10 megohms per volt rating---something that will be shown in the specifications.

For those sensors listed below that have ohms listed as the measurement item, disconnect the negative battery terminal and then the sensor harness connector and measure the sensor's terminals.

For voltage measurements, you can obtain test harnesses from any of the Corvette specialty catalog houses.

Before beginning your efforts, print the page along with this page so you can cross reference the code information with the sensor information.


Sensor	Measured Value
Engine Coolant Temperature Sensor	185 Ohms @ 210F, 3400 Ohms @ 68F, 7,500 Ohms @ 39 F
Engine Oil Temperature Sensor	185 Ohms @ 210 F, 3400 Ohms @ 68 F, 7,500 Ohms @39 F
Oil Pressure Sender/Switch	1 Ohms @ 0 PSI, 43 Ohms @ 30 PSI, 86 Ohms @ 60 PSI
Fuel Quantity Sender	0 Ohms @ Empty, 45 Ohms @ 1/2 Full, 90 Ohms @ Full
MAT (Manifold Absolute Temperature Sensor)	185 Ohms @ 210 F, 3400 Ohms @ 70 F, 15,000 Ohms @ 40 F
Outside Temperature Sensor	4400 Ohms @ 60 F, 2200 Ohms @ 85 F
In Car Temp Temperature Sensor	4400 Ohms @ 60 F, 2200 Ohms @ 85 F
MAF (Mass Air Flow) Sensor	.4 Volts @ idle, 5 Volts @ Full Throttle
Oxygen (O2) Sensor	.1 Volt Lean Mixture, .9 Volt Rich Mixture
TPS (Throttle Position Sensor)	.54 Volts Idle, ~ 5 Volts Full Throttle

Sensor	Location
Engine Coolant Temperature Sensor	Front of engine, below Throttle Body
Engine Oil Temperature Sensor	Left rear of engine, just above the oil filter
Oil Pressure Sender/Switch	Top, left hand rear of engine
Fuel Quantity Sender	Top of fuel tank, beneath filler pipe escutcheon panel
MAT (Manifold Absolute Temperature Sensor)	Underside of manifold air plenum at rear
Outside Temperature Sensor	Right side of engine, top right corner of radiator
In Car Temp Temperature Sensor	Coupe: above left seat near interior courtesy light, Convertible: center of cargo compartment lid
MAF (Mass Air Flow) Sensor	Front of engine ahead of throttle body
Oxygen (O2) Sensor	Left side of engine, in exhaust pipe
TPS (Throttle Position Sensor)	Right side of throttle body at the front