MBE 900 DDEC VI Troubleshooting – SPN 158/FMI 2 Unmatched MCM and CPC Signals

SPN 158/FMI 2

This diagnostic is typically unmatched MCM and CPC signals.‪

MCM and CPC Signals Check

Check as follows:‪

1. Check for multiple codes.
   1. If fault codes 158/2 and 168/0 are both still active, refer to “32.1 SPN 168/FMI 0” .
   2. If fault codes 158/2 and 158/1 are both still active, refer to “32.2.1 Battery Voltage Switched – Low”
   3. If fault codes 158/2 and 158/0 are both still active, refer to “32.1.1 Battery High Voltage Check” .
   4. If fault codes 158/2 and 168/1 are both still active, refer to “32.2 SPN 168/FMI 1” .
   5. If only fault code 158/2 is present, go to step 2 .
2. Measure the difference in voltage inputs between the CPC and the MCM. See Figure “Power Wiring” .
   1. If the voltage difference is less than 1.0 V, contact the Detroit Diesel Customer Support Center (313–592–5800).
   2. If the voltage difference is greater than 1.0 V with the CPC indicating the low voltage, go to step 3 .
   3. If the voltage difference is greater than 1.0 V with the MCM indicating the low voltage, go to step 4 .

Figure 1. Power Wiring

• Replace or repair the bad contacts and/or voltage supply for pins 2/3 (ignition) and 2/2 (ground) of the CPC #2 connector. Refer to “32.3.1.1 Verify Repairs” .
• Replace or repair the bad contacts and/or voltage supply for pin M21/7 (power) and pins M21/5, M21/6, M21/8, and M21/9 (ground) on the MCM 21-pin connector. Refer to “32.3.1.1 Verify Repairs” .