8206code.fm Page 87 Tuesday, July 7, 1998 11:57 AM
DIAGNOSTIC CODE 3-5 (BASIC) Test 10
Test 18
Checking the control valve gasket
Checking for a defective V-MAC II module 1. Replace the V-MAC II module with a new module, or with a module from another truck. DO NOT REPROGRAM THE MODULE AT THIS TIME. 2. Run the engine at 800 rpm for at least 30 seconds and record the timing.
If the timing on the diagnostic tool is the same as the static timing (within 1 degree), the old V-MAC II module was defective. Install a new V-MAC II module. If the timing on the diagnostic tool disagrees with the static timing by more than 1 degree, reinstall the original V-MAC II module. A potential flywheel problem may exist. Call Service Engineering.
Figure 138 — Checking Control Valve Gasket
1. Remove the timing control valve and inspect the valve gasket.
Test 19 Checking static timing against the emissions plate
If the gasket is installed properly, proceed to Test 20.
If the static timing is more advanced than the number stamped on the emissions plate by more than 1 degree, proceed to Test 38.
If the gasket is not installed properly, correctly install a new gasket. Reinstall the timing control valve. Retest to be sure the problem has been corrected.
If the static timing is more retarded than the number by more than 1 degree, proceed to Test 39.
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