Diagnostic Aids

Enter this test only when all steps under QUICK TEST have been successfully completed and engine still does not start or if directed here from another test or chart. This test is only intended to diagnose:

Bi-fuel relay module.
Compuvalve.
Harness circuits.

NOTE: During bi-fuel diagnostics, intermittent failures are possible. Perform wiggle test and tap lightly on relays during testing.

1) Check Voltage To Bi-Fuel Relay Module

Turn ignition switch to OFF position. Disconnect bi-fuel relay module connector C4026. See Figure. Turn ignition switch to ON position. Measure voltage between bi-fuel relay module C4026 terminals No. 1, 2 and ground. If both measurements are more than 10 volts, go to next step. If any measurement is 10 volts or less, repair open or short in affected circuit.

2) Check Bi-Fuel Relay Module Fuse No. 1 (3-Amp)

Check bi-fuel relay module fuse No. 1 (3-amp). If fuse is okay, go to next step. If fuse is not okay, replace bi-fuel relay module fuse No. 1 (3-amp) and go to next step.

3) Check KAPWR Output From Bi-Fuel Relay Module

Disconnect bi-fuel relay module connector C4035. See Figure. Reconnect bi-fuel relay module connector C4026. See Figure. Measure voltage between bi-fuel relay module C4035 terminal No. 8 and ground. If voltage is more than 10 volts, go to next step. If voltage is 10 volts or less, replace bi-fuel relay module.

4) Check Bi-Fuel Relay Module Fuse No. 2 (10-Amp)

Check bi-fuel relay module fuse No. 2 (10-amp). If fuse is okay, go to next step. If fuse is not okay, replace bi-fuel relay module fuse No. 2 (10-amp) and go to next step.

5) Check VPWR Output From Bi-Fuel Relay Module

Turn ignition switch to OFF position. Ensure bi-fuel relay module connector C4035 is disconnected and bi-fuel relay module connector C4026 is reconnected. Turn ignition switch to ON position. Connect a jumper wire between bi-fuel relay module harness connector C4035 terminal No. 10 and ground. Measure voltage between bi-fuel relay module harness connector C4035 terminals No. 1, 2, 3, 4, 6, 7 and ground. See Figure. If all measurements are more than 10 volts, go to next step. If any measurement is 10 volts or less, replace bi-fuel relay module.

6) Check Compuvalve Main Harness

Turn ignition switch to OFF position. Disconnect compuvalve connector C4025. See Figure. Ensure bi-fuel relay module connector C4035 is disconnected. Check for continuity between bi-fuel relay module harness connector C4035 terminal No. 10 and ground. Check for continuity between compuvalve and bi-fuel relay module harness connector terminals listed in COMPUVALVE MAIN HARNESS RESISTANCE TEST table. If continuity exists at each terminal, replace compuvalve. If continuity does not exist at one or more terminals, replace compuvalve main harness.

COMPUVALVE MAIN HARNESS RESISTANCE TEST

Compuvalve Harness Connector C4025 Terminal No.

Bi-Fuel Relay Harness Connector C4035 Terminal No.

9 ⁽¹⁾

⁽¹⁾	F-Series only.