Series 60 DDEC V Troubleshooting

Section 27.2 Troubleshooting Flash Code 21, PID 91/FMI 3

Section 27.2
Troubleshooting Flash Code 21, PID 91/FMI 3

This diagnostic condition is typically:‪

  • Open sensor return circuit
  • Sensor signal circuit is shorted to the sensor +5 volt supply

Refer to "27.2.1 General Throttle Information (Automotive Limiting Speed Governor)" for general throttle information. Refer to "27.2.2 Multiple Code Check" to begin troubleshooting.‪

Section 27.2.1
General Throttle Information (Automotive Limiting Speed Governor)

The correct TPS/AP Sensor counts for DDEC V engines at idle should be 64 - 205 counts.‪

  • Typical DDEC foot pedals today, at idle, provide 90–175 counts.
  • The DDEC system will log a TPS/AP Sensor low volt code (PID 091, FMI 4, Flash Code 22) if the TPS/AP Sensor counts go below 48.
  • The DDEC system will log a TPS/AP Sensor high volt code (PID 091, FMI 3, Flash Code 21) if the TPS/AP Sensor counts go above 968 counts.
  • In order to go from 0% to 100% throttle, the counts have to increase 546 above the idle count, or 100 counts, whichever is greater.
  • If an idle validation switch (IVS) is configured, to go from 0% to 100% throttle, the counts have to increase 546 above the counts at which the IVS opens or 100 counts, whichever is greater.
  • If 0% throttle is attained with the foot off the pedal, and if 100% throttle is attained with the pedal to the floor, then the pedal should not be considered a factor for low power complaints.

Section 27.2.2
Multiple Code Check

Perform the following steps to check for multiple codes.‪

  1. Turn ignition ON.
  2. Plug in diagnostic tool and read the active codes.
    1. If active code 91/3 and no other active codes are logged, refer to "27.2.3 Sensor Check" .
    2. If any or all of the following codes are logged, p 91/3, p 91/4, p 187/3, p 100/3, refer to "80.1 Troubleshooting the Vehicle Interface Harness +5 Volt Supply" .
    3. If any codes except p 91/3 are logged, refer to "27.2.4 Return Circuit Check" .

Section 27.2.3
Sensor Check

Perform the following steps to check the sensor.‪

  1. Turn ignition OFF.
  2. Unplug the TPS/AP Sensor connector.
  3. Turn ignition ON.
  4. Read for active codes.
    1. If active code p 91/3 and any other codes are logged, refer to "27.2.8 Check for Short" .
    2. If code p 91/4 is logged, refer to "27.2.4 Return Circuit Check" .

Section 27.2.4
Return Circuit Check

Perform the following steps to check the return circuit.‪

  1. Turn ignition OFF.
  2. Install a jumper wire between pin A (return #952) and pin B (signal #417) of the TPS/AP Sensor harness connector.
  3. Disconnect the vehicle harness connector at the ECM/ECU.
  4. Measure resistance between sockets V-60 and V-13 on the vehicle harness connector. For Throttle Position Sensor schematic, See Figure "Throttle Position Sensor" .
    1. If the resistance measurement is less than or equal to 5 Ω, refer to "27.2.5 Check Throttle Position Sensor Adjustment" .
    2. If the resistance measurement is greater than 5 Ω, and the return line V-60 is open, repair the open and refer to "27.2.9.1 Verify Repairs" .
    3. Click to see this graphic in a separate window

      Figure 1. Throttle Position Sensor

Section 27.2.5
Check Throttle Position Sensor Adjustment

Perform the following steps to check for TPS/AP Sensor adjustment.‪

  1. Reconnect vehicle harness connector and plug in the TPS/AP Sensor.
  2. Hook up your diagnostic tool and select Throttle Sensor Display.
  3. Measure Throttle Counts at both no throttle and full throttle. Take several readings.
    1. If TPS/AP Sensor counts are ever greater than 968 counts, refer to "27.2.6 Throttle Position Sensor Adjustment" .
    2. If TPS/AP Sensor counts stay less than 968 counts, refer to "27.2.7 Check Throttle Position Sensor Connectors" .

Section 27.2.6
Throttle Position Sensor Adjustment

Perform the following steps to attempt TPS/AP Sensor adjustment.‪

  1. Check for pedal or linkage interferences.
  2. Loosen the TPS/AP Sensor screws and attempt to adjust for the correct throttle reading (64 - 205 counts). Do not attempt to adjust by bending the pedal mechanism.
  3. Recheck counts at idle and at full throttle.
    1. If the throttle counts are not correct, refer to "27.2.7 Check Throttle Position Sensor Connectors" .
    2. If the throttle counts are now correct, refer to "27.2.9.1 Verify Repairs" .

Section 27.2.7
Check Throttle Position Sensor Connectors

Perform the following steps to check the TPS/AP Sensor connectors.‪

  1. Check terminals at the TPS/AP Sensor connector (both sensor and harness side) for bent, corroded and unseated pins or sockets. See Figure "Throttle Position Sensor" .
    Click to see this graphic in a separate window

    Figure 2. Throttle Position Sensor

    1. If the terminals or connectors are damaged, repair both and refer to "27.2.9.1 Verify Repairs" .
    2. If the terminals or connectors are not damaged, replace the TPS/AP Sensor; refer to "27.2.9.1 Verify Repairs" .

Section 27.2.8
Check for Short

Perform the following steps to check for a short.‪

  1. Turn ignition OFF.
  2. Disconnect the vehicle harness connector at the ECM/ECU. Unplug the TPS/AP Sensor connector.
  3. Read resistance between sockets V-13 and V-11 on the vehicle harness connector. For ECM/ECU vehicle harness connector, see Figure "ECM/ECU Vehicle Harness Connector" .
    1. If the resistance is greater than 100 Ω or open, refer to "27.2.9 Check for Short to Battery" .
    2. If the resistance is less than or equal to 100 Ω, the signal line (V-13) is shorted to the vehicle +5 volt line (V-11). Repair the short and refer to "27.2.9.1 Verify Repairs" .
    3. Click to see this graphic in a separate window

      Figure 3. ECM/ECU Vehicle Harness Connector

Section 27.2.9
Check for Short to Battery

Perform the following steps to check for a short to the battery.‪

  1. Remove both fuses to the ECM/ECU.
  2. Disconnect the vehicle harness connector at the ECM/ECU.
  3. Measure resistance between socket V-13 on the vehicle harness connector and the power sockets V-61 and V-65. See Figure "ECM/ECU Vehicle Harness Connector" .
    1. If the resistance is greater than 100 Ω, go to step 4 .
    2. If the resistance is less than or equal to 100 Ω, a short exists between sockets where less than 100 Ω resistance was read. Repair short and reinsert fuses. Refer to "27.2.9.1 Verify Repairs" .
    3. Click to see this graphic in a separate window

      Figure 4. ECM/ECU Vehicle Harness Connector

  4. Check terminals at the ECM/ECU harness connector (both ECM/ECU and harness side) for bent, corroded and unseated pins or sockets. See Figure "ECM/ECU Vehicle Harness Connector" .
    1. If terminals and connectors are damaged, repair them. Refer to "27.2.9.1 Verify Repairs" .
    2. If terminals and connectors are not damaged, refer to "27.2.9.1 Verify Repairs" , to review this section. If review leads back here, install a test ECM/ECU or contact Detroit Diesel Customer Support Center (313–592–5800).
Section 27.2.9.1
Verify Repairs

Perform the following steps to verify repairs.‪

  1. Turn ignition OFF and reconnect all connectors.
  2. Turn ignition ON and clear diagnostic tool codes.
  3. Start and run the engine for one minute. Check idle position and full throttle.
  4. Stop engine.
  5. Check diagnostic tool for codes.
    1. If no codes are displayed, troubleshooting is complete.
    2. If code p 91/3 is not logged, and other codes are logged, refer to "18.3 First Step for Diagnosing a Fault Within the DDEC System" .
    3. If code p 91/3 is logged, and other codes are logged, all system diagnostics are complete. If a problem still exists, review this section from the first step to troubleshoot the error, refer to "27.2.2 Multiple Code Check" .


Series 60 DDEC V Troubleshooting Guide - 6SE570
Generated on 10-13-2008

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