DDEC III/IV Single ECM Troubleshooting – Section 10.5 No Data to Diagnostic Data Reader

Section 10.5
No Data to Diagnostic Data Reader

Before using this procedure, all basic mechanical checks and physical inspections should have been performed with no problem found. Also the diagnosis of the DDEC system in Section 9 referred you to this section.‪

Section 10.5.1
Read Codes on the Check Engine Light

Perform the following steps to read the codes on the CEL or SEL:‪

1. Unplug the DDR.
2. Ignition should be ON; engine not running.
3. Enable diagnostic request switch.
4. Read codes flashing on the CEL and SEL.
   1. If codes are flashing out, refer to "10.5.4 Check for Open" .

   Note: If you wish to bypass diagnosis of a potential data line of the DDR problem for now, diagnose the active code by referring to the section that matches the code number.

   2. If CEL and SEL are not flashing out codes, refer to "10.5.2 Check Diagnostic Request Circuit" .

Section 10.5.2
Check Diagnostic Request Circuit

Perform the following steps to check the diagnostic request circuit:‪

1. Ensure ignition is ON.
2. Plug in DDR.
3. Select Calibration Configuration.
4. Determine port assigned to Diagnostic Request on the ECM input switches.
5. Go to switch light status.
6. Depress and hold the diagnostic request switch.
7. Read status of diagnostic request.
   1. If the switch reads OFF, the diagnostic request circuit (#528) is open or the ground is poor or open. Repair the open circuit or the bad ground. Refer to "10.5.8 Verify Repairs" .
   2. If the switch reads ON, refer to "10.5.3 Check ECM Connectors" .

Section 10.5.3
Check ECM Connectors

Follow this procedure to check the ECM connectors:‪

1. Check the terminals at the vehicle harness and 5-way power harness connectors (both ECM and harness side) for damage: bent, corroded and unseated pins or sockets. See Figure "ECM Vehicle Harness Connector" .
   1. If terminals and connectors are okay, replace the ECM. Refer to "10.5.8 Verify Repairs" .
   2. If the terminals and connectors are damaged, repair them. Refer to "10.5.8 Verify Repairs" .
   

   Figure 1. ECM Vehicle Harness Connector

Section 10.5.4
Check for Open

Perform the following steps to check for an open:‪

1. Turn ignition OFF.
2. Place a jumper wire across pins A (#900) and B (#901) of the DDL connector. Unplug the vehicle harness connector and measure resistance between sockets C1 and C2.
3. Turn ignition ON, and again measure resistance between sockets C1 and C2. See Figure "Diagnostic Connector" .
   1. If both readings are greater than 5 Ω , one or both data wires (circuit #900 or #901) are open. Repair the break and refer to "10.5.8 Verify Repairs" .
   2. If either reading is less than 5 Ω, refer to "10.5.5 Check for Short" .
   

   Figure 2. Diagnostic Connector

Section 10.5.5
Check for Short

Perform the following steps to check for a short:‪

1. Remove the jumper wire from the DDL connector.
2. Measure resistance between sockets C1 (#901) and C2 (#900) of the vehicle harness connector.
   1. If the resistance measurement is less than 5 Ω, two data wires (circuit #900 or #901) are shorted together. Repair the short and refer to "10.5.8 Verify Repairs" .
   2. If the measured resistance is greater than 5 Ω, refer to "10.5.6 Check for Short to Ignition and Ground" .

Section 10.5.6
Check for Short to Ignition and Ground

Perform the following steps to check for a short to ignition and ground:‪

1. Remove all jumpers for the DDL connector.
2. Measure resistance between sockets A (#900) and C (ignition switch), A (#900) and E (ground), B (#901) and E (ground), and B (#901) and C (ignition switch) of the DDL connector.
   1. If the measured resistance is less than 5 Ω on any reading, a short exists between the data wires and ignition or ground. Repair the short and refer to "10.5.8 Verify Repairs" .
   2. If the measured resistance is greater than 5 Ω, refer to "10.5.7 Check Diagnostic Data Reader on Another Engine" .

Section 10.5.7
Check Diagnostic Data Reader on Another Engine

Follow this procedure to check the DDR on another engine:‪

1. Connect the DDR to another engine and read any parameter in the menu.
   1. If the procedure worked okay, refer to "10.5.8 Verify Repairs" .
   2. If the procedure did not work, the DDR is probably defective. Refer to the DDR instruction manual for repair.

Section 10.5.8
Verify Repairs

Perform the following steps to verify repairs:‪

1. Turn ignition OFF.
2. Reconnect all connectors.
3. Turn ignition ON.
4. Clear codes.
5. Turn ignition OFF.
6. Turn ignition ON.
7. Note status of CEL.
8. Start and run the engine for one minute.
9. Read inactive codes.
   1. If the DDR display reads NO DATA BEING RECEIVED FROM DATA LINK or DDEC SYSTEM NOT RESPONDING, all system diagnostics are complete. Review this section from the first step to find the error. Refer to "10.5.1 Read Codes on the Check Engine Light" .
   2. If the engine starts and no codes are read on the DDR, repairs are complete.
   3. If the engine starts and code displays, refer to "9.1 First Step for Diagnosing a Fault Within the DDEC System" .