TM   9-2320-273-20 Table 5-4. Engine Retarder Control Circuit Troubleshoot ting. 1 2 3 4 5 6 7 INSTRUCTION INDICATION NO   RETARDING   ACTION. With   ENGINE   RUN 12  volts  dc  nominal. switch  on,  check  for voltage  to  retarder foot   switch   (circuit 52A). Check  for  voltage  at circuit   52B   terminal of   foot   retarder switch. Check  for  voltage  at circuit   52C   terminal of  transmission  pres- sure switch. Check  for  voltage  at circuit   52D   terminal of  transmission  pres- sure switch. Check  for  voltage  at circuit   52E   terminal of   throttle   position sensing  switch. Check  for  voltage  at circuit   52F   terminal of   throttle   position sensing switch. Check  for  voltage  at circuit   52G   terminal of  panel  ENGINE RETARDER   switch. YES NO REMARKS Go to Step 2.  Check  for faulty   cir- cuit   breaker (para 5-5 C), NOTE Before making the voltage checks de- scribed in steps 2 through 8, do the following: Apply parking brake. Check system air pressure. Activate  transmission  control  group. Put transmission in gear. Press and hold engine retarder foot pedal during  voltage  checks. 12  volts  dc  nominal. 12  volts  dc  nominal. 12  volts  dc  nominal. 12  volts  dc  nominal. 12  volts  dc  nominal. 12  volts  dc  nominal. Go to Step 3 Go to Step 4 Go to Step 5 Go to Step 6 Go to Step 7 GO to Step 8 Replace switch. Repair  wir- ing between 52B and 52C. Drain  sys- tem  air pressure and replace switch. Repair  wir- ing  (52D, 52E)  or connection! Replace switch. Repair  wir- ing  (52F, 52G)  or connection: Change 2 5-33