Engine Controls - Correct Fault Code 18 Diagnosis
90porsche06 September 18, 1990Subject: RDK Fault Code # 18
Model Group
928 S4/GT 4
Part Identifier Number
4434 9009
ATTENTION: Service Manager/Service Technician
Models Affected: 928 S4, GT from model year 1990
Concern: Diagnostic work on RDK system using Porsche system tester 9288.
Service Information: The last sentence on page 44-305 of the 928 Workshop Manual states in effect:
"The following display
Data lead - RDK combi instrument - open circuit - not present (fault code 18.)" may appear as a fault output on control unit version R00, although there is not a fault.
This is possibly a system related code and may not indicate a malfunction.
Repair Hints: Fault code # 18 may also accompany other fault codes when they appear.
1. If the RDK warning light is not ON and code # 18 is the only fault readout on the 9288 tester, there is no fault.
2. If the RDK warning light is ON and code # 18 is the only fault readout, there is a fault. Repair problem and erase fault memory.
3. If the RDK warning light is on and fault code # 18 is one of two or more faults, correct the fault(s) other than # 18 and erase the memory.
If the warning light remains out during the road test, code # 18 does not exist.