X80 - DTC 1481: Check Power-to-High Fan and B(+) to HFC Relay

Continuous Memory Diagnostic Trouble Code (DTC) 1481 indicates that sometime while the high speed fan was On, the Fan Monitor (FANM) circuit went low.

NOTE: For one speed fan applications, disregard DTC 1481.

Possible Causes:
- Open in Power-to-High Speed Fan circuit between the B(+) supply to the CCRM and the splice in the cooling fan.
- Open in B(+) circuit to CCRM (HFC relay).

- Key Off.

- Scan Tool connected.

- Disconnect cooling fan connector.

- Connect a non-powered test lamp between the Power-to-High Speed Fan circuit and ground circuit at the cooling fan vehicle harness connector.

- Key On, Engine Off.

- Access Output Test Mode on Scan Tool.

- Command High Speed Fan On.

- Observe test lamp for an indication of a fault while performing the following (the lamp will turn off when a fault is detected, indicating an open):
- Shake, wiggle, bend the Power-to-High Speed Fan circuit between the CCRM and the cooling fan.
- Shake, wiggle, bend the B(+) circuit between the B(+) supply and the CCRM (Pins 3 and 4).
- Lightly tap on the CCRM to simulate road shock.

- Connect DVOM between the Power-to-High Speed Fan pin and ground pin at the fan connector.

- DVOM set to measure resistance.

- Observe DVOM for an indication of an open circuit while performing the following:
- Shake, wiggle, bend the fan harness (if applicable).
- Lightly tap on the cooling fan to simulate road shock.

- Is a fault indicated?

YES -- ISOLATE fault and SERVICE as necessary. Complete PCM reset to clear DTCs. Clearing Diagnostic Trouble Codes

Rerun quick test. Diagnostic Subroutines (DSR) - Extracting Codes

NO -- GO to Pinpoint Test Step Z1 with the following data: FANM and HFCA PIDs (to verify when high speed fan is commanded on) and list of Possible Causes. Z1 - Intermittent Test Procedure