2001 Jeep Grand Cherokee Laredo P1491 Code: Cooling Fan Relay Circuit Issue - Diagnosis and Fix

Hi! First, does the radiator fan actually turn on? Just because your vehicle doesn't overheat doesn't mean the fan isn't working. Second, what scanner are you using? The P1491 code definition can vary by model year and vehicle configuration—some scanners may misinterpret or mislabel it.

Yes, the fan turns on when the engine reaches operating temperature and runs for a few minutes after shutdown before cycling off. This behavior didn't occur previously. I found loose wires and corroded ground connections during repairs. After fixing these issues and recharging the A/C system, the fan operates normally. Thanks for your input!

Yes, the fan activates at around 200°F and turns off after engine shutdown—this behavior was not present before. I identified loose wires and corroded grounds during repairs. After replacing wiring and grounding components, the fan runs properly. Thanks for your help!

I apologize for posting twice. My scanner is an Actron OBD-II device—it only allows me to clear the check engine light and does not offer advanced diagnostics like actuator testing.

The fan doesn't have an actuator test function on your scanner, which limits diagnostic accuracy. While the code description may be correct, I suspect either a broken cooling fan circuit or a damaged wire. If the vehicle has had any front-end collision, check for frayed wires to the relay. Use an ohmmeter to verify resistance in the fan circuit. Have you checked all fuses in the vehicle?

The original fan was running but drawing 8 amps—excessive current that caused wiring and relay components to overheat. I replaced both the fan motor and the wiring harness leading to the relay, as well as the relay itself. After performing an ohmmeter test, I confirmed the new circuit draws less than 1 amp. The fan now operates correctly. However, the P1491 code persists. It returns after clearing it on startup. I'm not sure if you're suggesting additional steps—I don't have access to actuator testing. My scanner provides freeze frame data and sensor readings (including O2 sensors), but 'inc' means inconclusive—this is the only emission-related note from the scan.

I'm referring to a high-quality scan tool with bi-directional control—the ability to manually activate the fan. This helps confirm whether the actuator (fan motor) is functioning properly and not seized or drawing excessive current. Standard OBD-II readers cannot perform this test. Since you've rewired the circuit and replaced the relay, I'd like to ask again: Does the fan turn on at around 200°F? Did you verify it with a jumper lead or wait for natural cycling? If the code returns immediately after startup, it likely indicates that the Powertrain Control Module (PCM) detects a faulty relay—especially if aftermarket parts are used. Note: The 2001 Jeep Grand Cherokee uses a solid-state relay driven by PWM signals from the PCM. Many low-quality aftermarket relays or components (like O2 heater modules) generate P1491 codes even when circuits are intact because they're incompatible with the PCM's signal requirements. I don't doubt your old fan was defective, but I need more details: which parts were purchased? How were they wired? Does the fan activate at 200°F? And what about grounding and wiring integrity?

The fan activates when engine temperature reaches approximately 200°F as shown on the dashboard gauge. It turns off after shutdown and cycles back on several minutes later. I inspected all accessible wires during front-end repairs multiple times before reassembling. The large-gauge wire to the relay consistently reads 12.4 volts even without ignition—indicating a constant power source. The two center wires connect directly to the fan, with an ohmmeter reading of 0.4 ohms. The smallest wire had several nicks and was replaced as much as possible.

Where did you purchase the relay from?

I bought it from AutoZone.