I’ve encountered many a sweeping change in my 40 years of automotive experience, and I’ve heard complaints from both sides of the service aisle about why manufacturers think they have to keep changing things instead of leaving well enough alone. Well, as I used to tell the old timers, we could still be riding horses and rowing boats, I reckon. They complained about the move from contact points to electronic ignition, carburetors to fuel injection, and so on. Granted, there are some elements of our vehicles that seem to have been changed for the sake of change. Modules now take requests from switches and energize loads through relays, and many of those relays are now being integrated into the modules instead of being individually replaceable, which makes repairs unnecessarily expensive. For one example among hundreds, the fuse panel/junction box on a 2006 Sonata costs about $700 and contains several integral relays. And then there are those eggshell fragile “smart” junction boxes. The only piece of 21st century technology on my 100,000-mile 2007 Ford Taurus is the smart junction box, and it holds the distinction of being the only part of the vehicle that has ever given me any trouble.
Some of these “smart” boxes have labels stating that the module has to be replaced if it’s dropped from more than 20 centimeters. Networking abounds, and not only within the vehicle’s perimeter; nowadays when you pull your late-model car into the garage it may ask to connect to your home’s WIFI, and just about everybody has heard about the very troubling experiment where a couple of hackers were able to drive that Jeep into the ditch after having hacked its internet connection and taken control away from the driver.
All that being said, these sweeping changes will keep on sweeping, but people are still driving older cars that pre-date these changes, and those cars still need fixing. The good thing about the moderately older cars is that a lot of technicians have left digital bread crumbs in iATN and Identifix pointing us in the right direction, and there are TSBs that provide short cuts to some solutions that might otherwise take hours to troubleshoot. Newer platforms and those that are sparsely represented in the market have fewer recorded repairs, and they may require the technician to plow some new ground. To be frank, we can discover that we’ve been dreadfully spoiled by the databases and find ourselves troubled and plowing new ground if we can’t find a silver bullet among the posts.
Handling help requests
I get quite a few emails through my website asking for advice, and I sometimes get phone calls from shop owners and family members that live in other states. I wish I could say I have all the answers, and I try to answer the emails quickly, but there are times when the person making the request doesn’t give enough information and there are other times when I simply don’t have an answer for them. Sometimes the help request is super sparse, like those doggone work orders I used to get when I was at the dealer where the service advisor put the words “Runs rough” on the repair line and the car would perform just fine when I drove it, and then I’d discover the owner was talking about a mild tire balance concern at a certain speed on a certain stretch of road.
Sometimes, however, a savvy vehicle owner will articulate his or her concern very well and emails will be exchanged that bear fruit. For one example among many, I had an email exchange that went this way, and it had a happy ending:
"My car has started to hum at certain speeds. It's an automatic, but when it's in fourth gear, it starts to hum. Do you know what this could be?" Joe asked.
"What make, model, and year car is it?" I replied.
"It’s a Mazda 6 sedan, 2005. It hums when I'm up to 40 or 4th gear,” Joe said.
"Does it change with throttle angle or vehicle speed (remaining in 4th)? I asked.
"Yes, if I go past 40 it will start to hum pretty loudly.”
"If you swerve gently back and forth does the humming get quieter or stop? If so, it's probably a hub bearing." I wrote.
"You are amazing! I found it was the hub bearing. I went to a mechanic who tried to take advantage of me, and I was able to break down the symptoms and possible issue. He suddenly took me seriously. Thanks again!” Joe said.
This is a rather familiar kind of exchange – more than a few people email me with car trouble before they even take the problem to a shop, because they’ve been burned before and they’re trying to insulate themselves against being fleeced by a misdiagnosis or an unnecessary upsell. And while we know that not every shop is prone to try and take advantage of people, just about everybody reading these words knows that there are too many shops out there that don’t repair the problem and leave customers frustrated and angry. The other side of the coin is that there are some customers who are treated right that sometimes leave shop owners just as frustrated and angry because we all know that the customer is not always right. Sometimes they’re dead wrong and just want something for nothing. The magic is in being objective enough to know the difference between when we’re wrong and when they’re wrong, and our bottom line can be a strong motivator, but our good name is worth more than just about anything else we own. Sometimes it’s best to bite the bullet and satisfy the customer, because they will talk trash about you if they believe you did them wrong, even if it’s a gray area.
A call for the calf rope
This story begins with a help request from my youngest son Luke, who lives six hours away, is married with kids, and works as a computer network specialist for a very large company. Vehicles aren’t his area of expertise, but he’s a quick study and never quits working on something until he gets it fixed. To begin with, his Camry’s water pump locked up and destroyed the timing belt, but the 2.2L belt engine is a free-spinner, and so he had a wrench-smart friend replace the water pump and timing belt, but when his friend was turning the engine through by hand to check for proper timing after replacing the belt, it would reach a lock point like the piston was making contact with something.
“I’m going to have to pull the head,” he told Luke, “apparently it has bent some valves.” My son remembered hearing me say that it was a free-spinning engine and so he put his friend on the phone with me.
“That engine doesn’t bend valves,” I told him. “You’ve got something on the head of a piston.”
“Well, in that case I need to pull the head anyway,” his friend replied, and I agreed. He did, and found some of that powdery carbon had broken loose and piled up of the head of a piston, and that’s what was stopping the engine when he was turning it by hand.
The head was re-worked, the crud was cleaned, the gaskets were scraped, the head was reinstalled, and the engine began to breathe fire again, but the MIL almost immediately illuminated and while there wasn’t any black smoke, the gas mileage was in toilet territory, which defeated the purpose of getting this 16-year-old Camry back on the road. A code P0125 was set (engine too cold for closed loop), and the data stream scan revealed engine temps south of 160, so Luke replaced the thermostat and cleared the code, which immediately returned. He called me and said everybody he was talking to in his neck of the woods – including his mechanic friend – said the new thermostat had to be at fault, and the engine was indeed running only slightly warmer than it had previously. I’ve personally had to install three thermostats to get one good one, so I agreed. I wasn’t there to look at the rest of the data stream, but this code needed to be addressed before anything else was done. He went through a couple more Chinese-made parts store thermostats and then paid $25 for a really good one from Toyota, and while the engine temp was now hovering just above 200 degrees, the code kept returning. Remember, all this back and forth was happening via phone calls and photos sent via text message.
At that point I decided to punch the Camry into Identifix and discovered something I hadn’t encountered before — that some Toyotas of that vintage would throw the P0125 if for ANY reason the engine didn’t drop into closed loop – and that the majority of posted fixes revolved around replacing the “A/F sensor.” Obviously, if the sensor never comes alive, closed loop is a faraway dream, even with a warm engine, but the Toyota’s algorithms weren’t flagging any kind of O2 code, thus the confusion. This information is also briefly stated in the Toyota shop manual.
The Identifix post we perused in detail says, "Check the heater resistance of the A/F ratio sensor. It should have between 0.8 and 1.4 ohms,” which is just peachy if you’re working on a California car, but this one is a federal emission standard vehicle (I researched this afterward), and so when we found 13 ohms heater resistance, a new sensor was purchased – and Luke’s digital multimeter indicated that the new sensor’s heater resistance was almost the same as the old one. Quite predictably, the code returned.
At this point I told Luke we needed to make sure voltage and current were available at the sensor. I like to take an old sensor, clip the connector off, and wire a small low impedance light bulb into the O2 heater circuit in place of the sensor. Yeah, I know that most automotive instructors are terrified of even a low impedance test light, but I raked that rule off the table the first time a digital meter told me a voltage lie and caused me a couple of hours of work. At any rate, there was no voltage at all being delivered at the O2 connector with the key on OR the engine running. Now we were getting somewhere.
When you think you know
As with any circuit, understanding this one is important. Like most heater circuits, this one is hard-wired to power and receives its ground from the PCM, which typically keeps a close check on how much amperage the sensor is drawing. Let me also say here that in the late ‘90s, Toyota didn’t believe in putting circuit numbers or wire size tags on a schematic – all they put next to a wire is its color, and that can be annoying when you’re clicking from one schematic to the next looking for sources of voltage. The colorful wire trails and pin assignments are troublesome as well (see illustration).
With the connector in hand and my help, Luke identified the proper cavities at the harness connector, and we assayed to determine whether it was the ground or the power that was missing – as it turned out, one of the wires was broken right where it passes through the seal and goes into the connector to its terminal – but it was somewhat stealthy in the way it manifested itself. At first blush, a look at the place where the wires go into the connector seal looked just fine, but as the connector was rolled in his fingers, the broken wire pulled out, and we had hit pay dirt.
The brown wire on the schematic and in the photo is reference ground for the O2 sensor element, but has nothing to do with the heater. This broken wire was obviously the cause of the P0125 – since PCM is watching the voltage in relation to this ground and it wasn’t there, the O2 was flat as far as the PCM was concerned. Usually if you measure O2 voltage live on a groundless sensor you’ll see something that looks really high, like 2-3 volts, but the PCM won’t be able to see any voltage at all. And so Luke and his wrench-smart friend set about to make repairs – with butt connectors (face palm) and a pigtail they got from somewhere – the next thing that happened was a no-start, which brought another phone call, and I managed to vector them in to the right fuse, which turned out to be the fuse that feeds the EFI relay. With the replacement of that fuse, the no-start was handled, but the first time Luke drove the car to work the MIL returned, and when he got around to retrieving the DTC he discovered a P0135, which indicates that the O2 sensor heater is either pulling too much current or not enough.
This time he found a bad butt splice on the black/yellow wire that feeds the heater, thus the P0135. Once he got that straightened out, the MIL was gone and the gas mileage had returned.
It was a twisted path and everybody involved came out a little smarter on the other end. I just wish we could get rid of those butt connectors.
