8206noco.fm Page 186 Thursday, July 2, 1998 1:19 PM
SYMPTOM RELATED DIAGNOSTICS INCORRECT OIL PRESSURE VERSUS GAUGE
Figure 303 — Diagnostic Procedure Flowchart
Test 3 Electrical checks This diagnostic procedure is performed when the oil pressure recorded by V-MAC II (displayed on a diagnostic tool) does not agree with the oil pressure gauge in the cab.
Test 1 Checking the pressure gauge 1. Connect a gauge that is known to be accurate to the oil pressure gallery or oil pedestal with a hose. 2. Start and idle the engine. 3. Compare the pressure on the known good gauge with the pressure recorded by V-MAC II using a diagnostic tool.
If the pressures agree within 3 psi, the problem is with the gauge in the cab, or there is no problem. If the pressures do not agree at anytime within 3 psi, proceed to Test 3.
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1. Turn the ignition key to the OFF position. 2. Disconnect the engine harness from the oil pressure sensor. 3. Measure the resistance from harness connector pin A (the ground [−] line) to a good ground.
If the resistance between the ground [−] line and ground is greater than 20 ohms, make sure that there are no electrical devices (lights, heater motors, etc.) running in the cab. Find a new good ground and try again. If the resistance is still greater than 20 ohms, there is a break or bad connection somewhere between the harness connector pin A and J1A connector pin G2. Check for corroded terminals at the harness, bulkhead connector and J1A connector, and for evidence οf damaged wiring. If the resistance is less than 20 ohms, proceed to Blink Code 1-1 or 1-2 (Engine Oil Pressure Sensor).
