DDEC III/IV Single ECM Troubleshooting

Section 10.8 Fan Operational Concern (On/Off Type)

Section 10.8
Fan Operational Concern (On/Off Type)

This section covers only the DDEC controlled fan operation, (fan type single, dual or two-speed). If the function is assigned, see description of DDEC fan control logic, listed in Table "DDEC Fan Control Logic Description" .‪

Cavity

Wire #

Function

Output/Input

X#‪

#‪

Fan Control 1‪

Output - Required‪

X#‪

#‪

Aux. Fan Control‪

Input - Optional‪

X#‪

#‪

Fan Override‪

Input - Optional‪

Table 1. DDEC Fan Control Logic Description

Section 10.8.1
Digital Fan Operation

Items used in digital fan operation include:‪

  1. The ECM provides ground (output Fan Control 1) and should be wired such that when this cavity grounds, the fan should turn off. When the circuit goes open, the fan should turn on.
  2. When Aux. Fan Control is configured (input), this wire must be connected to battery ground, or the fan will always be on. Typically, this is used with an air conditioning pressure switch. High pressure opens this circuit, and turns the fan on for a minimum time that can be set with the programming station on later ECM software versions.
  3. Fan Override - Grounding this wire will turn the fan on. This would normally be an OEM supplied switch on the dash.

Other than these items, the ECMs fan control output opens, turning the fan on due to engine temperatures that are above the programmed limits. Once a fan output turns the fan on for whatever reason, all fan off temperatures must be met before the fan will turn off. ‪

Temperatures for most highway applications are listed in Table "Highway Application Temperatures" .‪

Fan Control

Actual Fan Status

Coolant Temp

Oil Temp

Air Temp

Fan Control - 1‪

Fan ON‪

96°C / 204°F‪

110°C / 230°F‪

66°C / 150°F‪

Fan Control - 2‪

Fan ON‪

98°C / 208°F‪

113°C / 235°F‪

N/A‪

Fan Control‪

Fan OFF‪

92°C / 197°F‪

104°C / 219°F‪

49°C / 120°F‪

Table 2. Highway Application Temperatures

These temperature limits are only changeable in the base calibration.‪

Section 10.8.2
Check Output Status

Perform the following steps to troubleshoot a fan operation problem:‪

  1. Start engine.
  2. Ensure the air conditioning of the vehicle is OFF.
  3. Run engine for at least three minutes.
  4. Plug in DDR.
  5. Select switch / light status.
  6. Check the status of the Fan Control #1 while noting the actual fan status as listed in Table "Troubleshooting Fan" .

    Status

    Status

    Status

    Status

    Status

    Fan Control #1‪

    ON/GND‪

    OFF/OPN*‪

    OFF/OPN‪

    ON/GND‪

    OFF/OPN‪

    Actual Fan State‪

    OFF‪

    ON‪

    ON‪

    ON‪

    OFF‪

    Refer to "10.8.3 Fan Information"

    Refer to "10.8.3 Fan Information"

    Refer to "10.8.4 Check Input Status"

    Refer to "10.8.7 Check for Output Open"

    Refer to "10.8.8 Check for Output Short"

    Table 3. Troubleshooting Fan

    * Hot engine

Section 10.8.3
Fan Information

The steps that led to this procedure do not indicate a problem with the fan control logic in the ECM. The fan operation is normal if the steps that you checked led you to this section.‪

The fan status is correct according to what the ECM is requesting.‪

If you believe the fan state should be different, review the DDEC application and installation manual for information on fan control configuration.‪

Section 10.8.4
Check Input Status

Read the status of the inputs used for fan operation listed in Table "Input Status" . (Note both together.)‪

Status

Status

Status

Aux. Fan Control‪

OFF/OPN‪

ON/GRD‪

ON/GRD‪

Fan Override‪

OFF/OPN‪

ON/GRD‪

OFF/OPN‪

Refer to "10.8.6 Check for Input Open"

Refer to "10.8.9 Check Override Request"

Refer to "10.8.3 Fan Information"

Table 4. Input Status

Section 10.8.5
Check Auxiliary Fan Control Request

Perform the following tests to check the auxiliary fan control switch:‪

  1. Turn A/C OFF and ignition ON.
  2. Is the auxiliary fan control status ON?
    1. If the auxiliary fan control is on, this should not request the fan on; this is normal. The fan may remain on for up to three minutes after auxiliary fan control is turned on.
    2. If the auxiliary fan control is off, check that a normally open pressure switch is not installed; then, refer to "10.8.6 Check for Input Open" .

Section 10.8.6
Check for Input Open

Perform the following tests to check for an open circuit:‪

  1. Turn ignition OFF.
  2. Disconnect vehicle 30–pin connector at the ECM.
  3. Turn ignition ON.
  4. Measure resistance between auxiliary fan control wire and a good ground.
    1. If the measured resistance is greater than 1,000 Ω, an open line exists in the auxiliary fan control wire, or auxiliary fan control is configured and not wired, or the switch is bad. Repair open line or replace the switch if an auxiliary fan control is used. If this feature is not to be used, disable the auxiliary fan control with the programming station. Refer to "10.8.11 Verify Repairs" .
    2. If the measured resistance is less than or equal to 1,000 Ω, refer to "10.8.10 Check Connectors" .

Perform the following steps to troubleshoot fan always on. The steps that led to this procedure do not indicate a problem with the fan control logic in the ECM. The fan operation is normal if the steps that you checked led you to this section.‪

Section 10.8.7
Check for Output Open

Perform the following steps to check for an output open:‪

  1. With ignition off, locate OEM supplied wire used for Fan Control #1.
  2. Determine where the wire terminates. (e.g. fan solenoid, relay, data module, etc.)
  3. Disconnect the Fan Control #1 wire at the solenoid/relay.
  4. Turn ignition ON.
  5. Measure resistance between the fan control #1 wire and a good ground, battery (-).
    1. If the measured resistance is greater than 48,000 Ω or open, an open circuit exists in the FC#1 wire. Repair the break. Refer to "10.8.11 Verify Repairs" .
    2. If the measured resistance is less than or equal to 48,000 Ω, refer to "10.8.10 Check Connectors" .

Section 10.8.8
Check for Output Short

Perform the following steps to check for an output short:‪

  1. With ignition off, locate OEM supplied wire used for Fan Control #1.
  2. Determine where the wire terminates. (e.g. fan solenoid, relay, data module, etc.)
  3. Disconnect the Fan Control #1 wire at the solenoid/relay.
  4. Measure resistance between the fan control #1 wire and a good ground, battery (-).
    1. If the measured resistance is greater than 1,000 Ω or open, refer to "10.8.10 Check Connectors" .
    2. If the measured resistance is less than or equal to 1,000 Ω, the output wire is shorted to ground, keeping the fan off. Repair the short or replace the wire. Refer to "10.8.11 Verify Repairs" .

Section 10.8.9
Check Override Request

Perform the following steps to check the fan override switch:‪

  1. Is the fan override switch on?
    1. If the fan override is on, and the fan override is requesting fan on, this is normal.
    2. If the fan override is not on, the fan override wire is shorted to ground, repair the short or re-configure the input if this is an error in programming. Refer to "10.8.11 Verify Repairs" .

Section 10.8.10
Check Connectors

Perform the following steps to check the connectors:‪

  1. Check connectors for damaged, bent, or corroded terminals.
    1. If the pins and terminals are not damaged, the problem may be due to the solenoid, ECM, or OEM device that operates the fan. Contact the OEM for further information or instructions. The ECM and wiring between the ECM and device appear to be operating correctly and in good repair. The ECM is requesting the fan operation correctly and the checks indicate the ECM and wire between the ECM and OEM device is okay.
    2. If the pins or terminals are damaged, repair or replace them. Refer to "10.8.11 Verify Repairs" .

Section 10.8.11
Verify Repairs

Perform the following steps to verify repairs:‪

  1. Connect any removed connectors.
  2. Start engine.
  3. Operate engine under conditions that brought you to this section.
  4. Check fan operation.
    1. If the fan operates correctly, troubleshooting is complete.
    2. If the fan does not operate correctly, review this section from the first step to find the error.


DDEC III/IV Single ECM Troubleshooting Guide - 6SE497
Generated on 10-13-2008

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