Suzuki GRAND VITARA XL-7 Owner's Manual page 223

6-1-62 ENGINE GENERAL INFORMATION AND DIAGNOSIS (H27 ENGINE)
Step
4 HO2S heater control circuit check :
1) With ignition switch OFF, install HO2S
heater relay.
2) With ignition switch ON leaving engine OFF,
check voltage between C51-2-4 and
ground.
Is the voltage 10 – 14 V?
Fig. for STEP 3
a. HO2S heater relay
Action Yes
Substitute a known-good
ECM (PCM) and recheck.
No
Faulty HO2S heater relay
or "BLK" wire open, "BLU"
wire open or shorted to
ground circuit
or
"GRY" wire open or
shorted to ground circuit.
If OK, substitute a known-
good ECM (PCM) and
recheck.