Radiator and A/C Condenser Fan Low Speed Circuit Troubleshooting
NOTE: Before doing any symptom troubleshooting, check for powertrain DTCs.
  1. Check the No. 18 (20 A) fuse in the under-hood fuse/relay box, and the No. 36 (10 A) fuse in the under-dash fuse/relay box.
Are the fuses OK?
YES -
NO -
Replace the fuses, and recheck. If fuses blow again, check for a short in the No. 18 (20 A) and No. 36 (20 A) fuses circuit.■
  1. Jump the SCS line with the HDS.
    NOTE: This step must be done to protect the engine control module (ECM) from damage.
  1. Disconnect ECM connector A (44P).
  1. Turn the ignition switch to ON (II).
  1. Measure the voltage between ECM connector A (49P) terminal No. 5 and body ground.
Is there battery voltage?
YES -
Go to Step 6 .
NO -
Repair open in the wires between the under-hood fuse/relay box and the ECM, or between the No. 36 (10 A) fuse in under-dash fuse/relay box and the under-hood fuse/relay box. If wires are OK, replace the under-hood fuse/relay box. ■
  1. Turn the ignition switch to LOCK (0).
  1. Connect the ECM connector A (49P) terminal No. 5 to body ground with a jumper wire.
  1. Turn the ignition switch to ON (II).
Do the A/C condenser and radiator fans run on low?
YES -
Check for loose wires or poor connections at ECM connector A (49P) terminal No. 5. If the connections are good, substitute a known-good ECM, and recheck. If the symptom/indication goes away, replace the original ECM. ■
NO -
Go to Step 16 .
  1. Jump the SCS line with the HDS.
    NOTE: This step must be done to protect the engine control module (ECM) from damage.
  1. Disconnect ECM connector A (44P).
  1. Turn the ignition switch to ON (II).
  1. Measure the voltage between ECM connector A (44P) terminal No. 4 and body ground.
Is there battery voltage?
YES -
Go to Step 13 .
NO -
Repair open in the wires between the under-hood fuse/relay box and the ECM, or between the No. 36 (10 A) fuse in under-dash fuse/relay box and the under-hood fuse/relay box. If wires are OK, replace the under-hood fuse/relay box. ■
  1. Turn the ignition switch to LOCK (0).
  1. Connect the ECM connector A (44P) terminal No. 4 to body ground with a jumper wire.
  1. Turn the ignition switch to ON (II).
Do the A/C condenser and radiator fans run on low?
YES -
Check for loose wires or poor connections at ECM connector A (44P) terminal No. 4. If the connections are good, substitute a known-good ECM, R18A2 engine, K20Z4 engine, and recheck. If the symptom/indication goes away, replace the original ECM, R18A2 engine, K20Z4 engine. ■
NO -
Go to Step 16 .
  1. Turn the ignition switch to LOCK (0).
  1. Disconnect the radiator fan 2P connector.
  1. Turn the ignition switch to ON (II).
  1. Measure the voltage between the radiator fan 2P connector terminal No. 2 and body ground.
Is there battery voltage?
YES -
Go to Step 20 .
NO -
Repair open in the wire between the under-hood fuse/relay box and the radiator fan. If the wire is OK, replace the under-hood fuse/relay box. ■
  1. Turn the ignition switch to LOCK (0).
  1. Reconnect the radiator fan 2P connector.
  1. Connect the radiator fan 2P connector terminal No. 1 to body ground with a jumper wire.
  1. Turn the ignition switch to ON (II).
Does the radiator fan run at high speed?
YES -
Go to Step 24 .
NO -
  1. Turn the ignition switch to LOCK (0).
  1. Disconnect the jumper wire from the radiator fan 2P connector.
Is the relay OK?
YES -
Go to Step 27 .
NO -
Replace the fan control relay.■
  1. Turn the ignition switch to ON (II).
  1. Measure the voltage between the fan control relay 5P socket terminal No. 1 and body ground.
Is there battery voltage?
YES -
Go to Step 29 .
NO -
Repair open in the wire between the radiator fan and the fan control relay.■
  1. Turn the ignition switch to LOCK (0).
  1. Disconnect the jumper wire from ECM connector A (49P) or ECM connecter A (44P).
  1. Disconnect the A/C condenser fan 2P connector.
  1. Check for continuity between the fan control relay 5P socket terminal No. 4 and the A/C condenser fan 2P connector terminal No. 2.
Is there continuity?
YES -
Go to Step 33 .
NO -
Repair open in the wire between the fan control relay and the A/C condenser fan.■
  1. Check for continuity between the A/C condenser fan 2P connector terminal No. 1 and body ground.
Is there continuity?
YES -
NO -
Check for an open in the wire between the A/C condenser fan and body ground. If the wire is OK, check for poor ground at G301. ■