When you've got a P0737 code staring back at you, it's your car's way of telling you the transmission isn't happy with the info it's getting about engine speed. In my experience, this trouble code usually shows up when the Transmission Control Module (TCM) isn't receiving a proper engine speed signal-something it absolutely depends on to shift gears smoothly. That signal typically comes from the Engine Speed Sensor (ESS), which you might also hear called the crankshaft position sensor or output speed sensor, depending on the vehicle. If that sensor starts sending weird data, goes silent, or the numbers just don't make sense, the TCM throws a fit-and that's when you see P0737. Over the years, I've seen this code crop up on all sorts of makes and models, from Hondas to Dodges. The fix can change depending on what you're working on, but the core problem's always the same: your transmission's just not getting the engine speed data it needs, and that throws off everything from shifting to how your car actually drives down the road.
DTC P0737
4867
7 minutes of readingCauses of P0737
Let me walk you through what I usually find behind a p0737 code. Nine times out of ten, it's an electrical gremlin. Here's the short list of culprits I've come across in the shop:
- A bad engine speed sensor (ESS)-these guys can fail outright or get so filthy they stop working right.
- Messed-up wiring or crusty connectors going to the ESS-think corrosion, frayed wires, or loose plugs that wiggle when you least expect it.
- A sensor pickup covered in gunk-metal shavings or road debris can stick to the sensor and throw off its readings.
- The TCM (or sometimes the ECM) itself acting up-rare, but I've seen it happen.
- Transmission fluid that's low or nasty-doesn't happen as often, but bad fluid can add to the problem or even damage the sensor over time.
When I'm chasing down this code, I always start by zeroing in on the sensor and its wiring. That's where the lion's share of problems seem to hide.
Symptoms Related to P0737 Engine Code
I've had customers come in with all sorts of complaints when this code is present. If you see P0737, you’ll probably notice a few telltale signs. Here’s what usually tips me off:
- Hard or jarring shifts-the transmission might slam into gear or drag its feet before shifting.
- Gas mileage takes a nosedive-you'll be visiting the pump more than you'd like.
- The engine won't start, or it stalls out of nowhere-sometimes it'll crank but not fire, or just quit while idling.
- Feels like you're driving with the parking brake on-sluggish acceleration and low power are common.
- Speedometer starts acting possessed-jumpy readings or numbers that don’t match your actual speed.
- The gas pedal feels dead-step on it, and the car barely responds.
If you're seeing more than one of these symptoms at once, that's a solid clue this code isn’t just a one-off hiccup.
Diagnosis Steps for OBD2 Code P0737
Want to know how I track down a obd2 code p0737? Here’s my go-to playbook:
- First thing’s first-always check for Technical Service Bulletins (TSBs) for your car. Sometimes the fix is already known, and it’ll save you hours in the garage.
- Next up, make sure the battery and alternator are up to snuff. Weird voltage can throw the whole system out of whack, so rule that out right away.
- Then I go straight for the engine speed sensor (ESS). If the car’s acting up or won’t start, I’ll test the sensor against the specs in the service manual. Off numbers? Time for a replacement.
- Don’t skip the transmission fluid. Check the level, look at the color, and smell it. If it’s dark, gritty, or smells burnt, swap it out. Stick with what the manufacturer recommends-trust me, shortcuts here cause headaches later.
- After that, inspect the wiring harness going to the ESS. Look for chafed spots, cuts, or any bit of green fuzz (corrosion) on the connectors. If you find something, fix or replace it before moving forward.
- Pull the ESS and give it a good cleaning. These sensors are magnetic, so metal shavings love to cling on and mess up readings. A quick clean can make all the difference.
- Last, check out the TCM itself. Sometimes it's bolted right to the transmission and gets hit with heat and moisture. Look for corroded pins or water damage-sometimes a simple cleaning is all it takes.
Work through these steps in order, starting with the basics. If the electrical stuff isn’t your cup of tea, don’t risk it-get someone experienced to lend a hand.
Common Mistakes When Fixing P0737 Code
I can’t tell you how many times I’ve seen folks throw money at the wrong problem. Here are the biggest slip-ups when tackling this code:
- Jumping to the expensive fix-swapping out the TCM or ECM-without first checking the sensor and wiring. That’s like buying a new TV because the remote batteries are dead.
- Forgetting to check the basics-ignoring fluid levels or battery health before tearing into the wiring or sensors.
- Missing out on dirty or corroded connectors-a little time spent cleaning can save you a lot of frustration.
- Dumping in the wrong transmission fluid-using anything other than what’s listed in the manual can create a whole new set of problems.
- Not looking up TSBs-sometimes there's a bulletproof fix out there and folks just don’t know about it.
Take it from me: always start simple and methodical. You'll save yourself time, cash, and a fair bit of swearing.
Seriousness of OBD Code P0737
Let me be straight with you-you really don’t want to brush off a P0737. Sure, maybe at first it’s just a rough shift or a wonky speedometer, but if you keep driving like that, you’re tempting fate. When the transmission isn’t getting accurate engine speed info, it can start shifting at all the wrong times, putting extra stress on the transmission parts. Left alone, I’ve seen this snowball into broken internals, fried modules, and sometimes even engine trouble. Plus, if your car starts stalling or refusing to start, you could find yourself stranded at the worst possible moment. Bottom line: deal with this code sooner rather than later. It’ll save you a pile of money and a mountain of headaches down the road.
Repair Solutions for P0737 Trouble Code
So, how do I fix a p0737 code? Here’s my usual process, depending on what the diagnostic uncovers:
- Swap out a bad engine speed sensor (ESS) if it’s not showing the right readings.
- Patch up or replace damaged wiring or connectors going to the ESS or TCM-no sense letting a broken wire take down the whole system.
- If the ESS is just grimy or covered in metal shavings, clean it up and pop it back in.
- Change out old, dirty, or burnt transmission fluid-always stick with what the manufacturer recommends, no exceptions.
- If, after all that, the TCM or ECM is still the problem (which is rare), replace or reprogram it as needed.
- Clear the code and take your car for a good test drive to make sure the fix stuck.
From what I’ve seen, cleaning or replacing the sensor, or fixing a wire, solves this most of the time. Replacing a control module? That’s almost always a last resort.
Conclusion
If there’s one thing to remember, it’s that P0737 spells trouble for your transmission’s ability to shift and drive right. This isn’t one of those codes you can just ignore and hope it goes away. Start with the basics-sensor, wiring, and fluid-and only move up to control modules if you really have to. Jumping on the problem early is the best way to keep your ride smooth and avoid a nasty repair bill later. If you’re not sure where to start, don’t be afraid to get a pro involved. Trust me-your transmission (and your wallet) will be glad you did.
