DTC 41

Code 41:

Ignition Wiring Diagram:

CODE 41

NO DISTRIBUTOR REFERENCE PULSE


Circuit Description:

Code 41 indicates that there are no distributor references pulses to the ECM with engine vacuum present. This code could be set with the key "ON," engine not running if the pressure sensor was indicating "engine running" voltage with just the key "ON." With a constant open or ground in the reference signal CKT 430, Code 12 would be set along with a 41. Use Code 12 chart if Code 12 and Code 41 are both set. Code 41 alone indicates the problem is intermittent. When the distributor reference line signal is lost, the engine runs full rich and with base spark timing. The result is poor performance, poor fuel economy, and possibly rotten egg odor from exhaust.


Test Description: Numbers below refer to circled numbers on the diagnostic chart.

1. Checks to see if pressure sensor voltage changes with loss of vacuum supply. A good sensor will change voltage across terminals "A" and "B" or ECM terminals "20" and "22" by 1 volt or more.

2. Checks for cause of an intermittent open or ground in the distributor circuit. A fault could also be an intermittent stuck pressure sensor that has the same voltage output as an "running" with only the key "ON," thus, no reference signal. Terminals must be removed from connectors to properly check them. The distributor pick-up coil should also be checked.


3. Since the voltage change was less than 1 volt, the problem is in the pressure sensor system. The ECM has "seen" engine running vacuum equivalent with no distributor reference signal, with the key "ON" and engine not running. If Code 12 is present with engine running, a distributor reference fault is indicated. See Code 12 chart first.