Why won't my Dodge Nitro start, or why does the horn go off by itself?

Short answer: On the Nitro, odd electrical behavior like the horn honking on its own, wipers or locks acting up, or a crank-but-no-start very often comes from the TIPM. That's the main fuse and relay box under the hood, with relays built onto a circuit board. A bad fuel pump relay inside it can keep the engine from starting. Test before you buy parts: owners check fuses, connections and grounds, and confirm power to the fuel pump.

Symptom: The engine cranks normally but won't fire, or nothing happens when you turn the key. You may also get a horn that sounds by itself, lights or wipers that come on, or locks that act up.

What to check first

1. Listen for the fuel pump humming for a couple of seconds at key-on. No hum points to the pump circuit.
2. Check the TIPM fuses and the battery connections and grounds. A weak battery or bad ground can mimic a TIPM failure.
3. Test for power at the fuel pump while cranking before replacing the pump or the TIPM.
4. Look at the TIPM plugs for corrosion or burned pins.
5. If it won't crank at all, have the starter circuit, the shifter position switch and the battery checked too. Owners found other causes there.

Likely causes

1. Failed relay inside the TIPM (fuel pump or starter). The relay is part of the TIPM's circuit board.
2. Battery, cable or ground problem. Cheap to rule out first.
3. Corroded TIPM plug or pins. Can cut power on and off.
4. Failed fuel pump or starter. Test the circuit first.

What it usually costs

We don't have reliable prices from owners in these threads. Repair specialists rebuild TIPMs, and remanufactured units cost less than a new dealer part. Testing first keeps you from buying a pump or starter you don't need.

Is it safe to keep driving?

A Nitro that won't start isn't dangerous, but a fuel pump relay that cuts out while driving can stall the engine. A horn or lights coming on by themselves can also drain the battery. Get it fixed before relying on the truck. Verify with a mechanic.

DIY or shop?

DIY for fuses, battery, grounds and simple tests with a test light or meter. TIPM replacement is plug-in, but used units must match your part number. Pump and starter work is easier at a shop.

Recalls, bulletins and complaints in plain words

• Recalls: NHTSA lists several Nitro recalls for these years. None that we found is for the TIPM. Check your VIN. If your truck is part of a recall, the dealer fixes it for free.
• NHTSA complaints: 391 keyword-matched complaints for Dodge Nitro 2007–2011 (of 1,454 unique complaints queried, NHTSA complaints API by model year, queried 2026-10-21; keywords: TIPM, fuel pump, no start, won’t start, crank, horn, stall, relay, power module). This counts complaints that mention these words. It is not a defect finding.

What owners report

• In Continuous crank no start on Nitro Forumz, an owner's Nitro cranked without starting. Members discussed checking the fuel pump circuit and the TIPM.
• In No crank - if it's not the TIPM what is it? on Nitro Forumz, an owner with a no-crank asked what else could cause it, a sign that not every Nitro no-start is the TIPM.

Quick tip

If a Nitro ever honks by itself in the driveway, take that as an early TIPM warning.

Vehicle focus: 2007–2011 Dodge Nitro.

Safety / mechanic note

A fuel pump that cuts out can stall the engine in traffic. Verify with a mechanic.