2007 Malibu MAXX Multiple Fault Codes

 Ok, they dropped off this 2007 Malibu. Complaints were stalling, low power, MIL, Reduced Power message, etc. When I went to drive the car into the shop it was doing all of the above so it seemed like a good time to look at codes and data. 

Engine P0106 | Manifold Absolute Pressure (MAP) Sensor Performance (Symptom 00) - Test Failed Since DTC Clear, Test Not Passed Since Power Up. 

P0107 | Manifold Absolute Pressure (MAP) Sensor Circuit Low Voltage (Symptom 00) - Current DTC, Test Failed Since DTC Clear, History DTC, Test Not Passed Since Power Up, Current DTC Since Power Up, Warning Indicator Requested. 

P0452 | Fuel Tank Pressure (FTP) Sensor Circuit Low Voltage (Symptom 00) - Current DTC, Test Failed Since DTC Clear, History DTC, Test Not Passed Since Power Up, Current DTC Since Power Up, Warning Indicator Requested. 

P0522 | Engine Oil Pressure (EOP) Sensor Circuit Low Voltage (Symptom 00) - Current DTC, Test Failed Since DTC Clear, History DTC, Test Not Passed Since Power Up, Current DTC Since Power Up. 

P0532 | Air Conditioning (A/C) Refrigerant Pressure Sensor Circuit Low Voltage (Symptom 00) - Current DTC, Test Failed Since DTC Clear, History DTC, Current DTC Since Power Up. 

P0641 | 5 Volt Reference 1 Circuit (Symptom 00) - Current DTC, Test Failed Since DTC Clear, History DTC, Test Not Passed Since Power Up, Current DTC Since Power Up, Warning Indicator Requested

A look at the scan data showed no MAP, FTP, Oil Pressure or A/C voltage from those sensors. Now what all those sensors have in common is they share a 5 volt reference circuit to be operable. The most likely possibilities here are that, (A) the engine computer is not outputting a reference voltage, (B) one of the sensors is shorting the reference voltage to ground, (C) the reference voltage circuit wiring is being shorted to ground at some point in the harness. The P0641 would set in any of those conditions. Now it was time to close shop, start here in the morning.

The next morning the car started and ran perfectly fine. Other than the MIL still on you would not know it had a problem. All of the previously dead sensors were now outputting voltage signals. My plan of attack was already decided though and this newest development wasn't changing it much. I would look at the harness and connectors as near each of the affected sensors as I could reasonably access. I didn't want to start by doing a lot of work, unless that became necessary. For instance, to gain unfettered access to some of the sensors/harness I would need to remove the grill, the upper intake, the power steering pump, heat shields, etc. I did poke and pull on harness in the area of each sensor and was not able to re-create the fault. While under the car checking the oil pressure switch harness it did seem a good time to look at the fuel tank harness before letting the car back down on the lift. The right front corner of the metal fuel tank shielding had sign of being hit in some manner and the harness just above that had a cut in the 5 volt reference circuit wire. The cut was laying on the sharp edge of the shield and occasionally shorting to ground. I had found the problem and repaired the wire, secured the harness in a better position, and cleared codes. 

 

Thanks for reading

Kenny@ggauto.repair

2006 Toyota Avalon V6-3.5L Misfire Complaint

 The customer complaint is a misfire. The check engine light is on and I'll check the stored engine codes. I can feel the misfire as I drive the car into the shop. Feels like one cylinder has dropped out. 

I got more that I was expecting. I was hoping for a code that would lead me to the misfiring cylinder without my having to check for myself. Instead I got misfire codes for every cylinder. 

I only currently have a misfire on one cylinder and I want to find that one since the problem exists now, while I am testing. I can't determine why there are misfires in the other cylinders while they are not misfiring. Work with what you are given. Now the scan tool can monitor current cylinder misfires so I looked there with the engine running and misfiring. I get something else that I wasn't expecting. I show no cylinders misfiring though it is indeed misfiring. 

 I'm left with determining which cylinder is misfiring by other means. Now, back in the old days I would disable a cylinder while the engine was running and listen for the rpm drop. No drop and there was the misfiring cylinder. When we had carbs and plug wires this was easiest to do by removing the plug wires one by one, either at the plug or at the distributor. Pull one, re-attach, pull next one and so on until you knew which cylinders were misfiring, or even weak contribution. As systems changed it turned to maybe disconnecting a coil, or an injector depending on what was easiest to access. The principal was the same. Kill that cylinder and pay attention to the rpms. (Remind me to tell you of grasping a plug wire on a Dodge Intrepid on a rainy day while standing in a puddle of water. I can tell you it is a very quick way to spot a bad plug wire.)

The process here is less intrusive and is done by commanding each injector to stop, one at a time, and note the rpm drop. (They call it commanding but it is more accurately, requesting.)  I found rpm drops on each cylinder tested except for #4. I found my misfire on #4 cylinder. Attached is the rpm drop with injector paused on #1. The rest would look similar so saving you the repetitive shots. I did want to include the misfiring #4 however a new wrinkle appeared. When I next started the car to get a screen capture during the test, it was no longer misfiring. It now became an intermittent misfire on #4 cylinder. At least I was able to find which cylinder was misfiring and I do know from the fact it is now not misfiring I don't have a compression or vacuum leak problem. I am looking at potentially an injector or ignition problem. I am leaning toward ignition since it does have the #4 ignition coil fault code stored as well. 

 The plan is to swap both the spark plug and coil from #4 with spark plug and coil from '#2 and see if the misfire moves to #2. This would be simpler if the misfire would return, versus my switching things while there is no misfire and waiting for it to come back. I gave the car several chances to miss and finally it did start to miss again prior to changing #2 & #4 coils and plugs. Here the miss if on #4. 

I removed both spark plugs and coils #2 & #4. The spark plugs are severely worn btw and I suspect are original with 211,066 miles. 

I swapped the #2 plugs & coils. If the misfire moves to #2 then the fault is definitely a bad coil and plug. 

Luckily I still have a misfire on re-start and it isn't on #4.

The misfire is now on #2. 

What will be needed here is new spark plugs and ignition coils. With the high mileage and worn plugs the coils have been stressed which caused the failure of #4. The rear plugs are very difficult to reach being under the intake manifold so the coils should be replaced at the same time to prevent having to go back and replace another failed coil very soon. 

Thanks for reading.

Kenny@ggauto.repair

845RE Park-by-wire malfunction Transmission Digest August 2024

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Codes vs Faults 2010 Dodge Ram

 This 2010 truck came in with three fault codes active. Instead of walking you through the testing, let's just go right to what was causing each code to set. 

Here they are: P0522, P1281 and P0456

P0522 was a leaking oil pressure sensor. 

P2181 was a poor connection at the coolant temperature sensor. 

P0456 was a bad gas cap seal. 

Now there was also a complaint of long cranking time at start, intermittently. These do have known problems with the fuel pump relay, which is built into the TIPM but the complaint could have also been caused by the poor coolant sensor connection. Since the problem hasn't appeared and since it could possibly be fixed via cleaning the connection, I've elected to do the wait and see option on that particular problem. 

Kenny@G&GAuto.Repair

Battery Drain Testing 2002 Dodge Ram

 This one gets a quick charging system check while it is running and looks good. 

I'll be disconnecting the battery for testing but want to keep the electrical system powered up so will connect the memory saver but first, just in case, I do a quick code scan. 

The battery tests good but the tester asked for me to verify the ambient temperature was above freezing which you don't usually see unless there is a questionable test result. Mental note made. It does need a full charge so going ahead with the charge while the battery is disconnected. 

Once the current draw was measured I did find excessive draw. I was told the truck was okay day to day but battery would drain over a weekend. This amount of draw would fit into that scenario. Once you find your draw you have to determine which circuit the draw is on. That is a matter, at first of removing fuses one at a time until you see the draw drop to an acceptable range. I found the problem was on fuse 4 of the underhood block. 

The odd thing about fuse 4 having the draw is that fuse feeds battery voltage directly to the ignition switch and doesn't feed power to anything until the switch is turned on. I suspected someone had been doing some accessory wiring or along those lines. 

I went right to the ignition switch and found someone had bypassed the ignition switch on that circuit and fed the power through a relay instead of through the switch. The problem was the relay was always on. The excessive draw was the relay. 

I'll need to repair the wiring and replace the ignition switch. Getting rid of that relay and going back to original design. 

Now we have an acceptable draw. 

Thanks for reading,

Kenny@GGAuto.Repair

Checking A/C on 1998 Dodge Ram 1500

 "The air conditioner isn't working" was the complaint on this older truck. A look under the hood at the visible parts of the system and I could see the clutch cycle switch had been leaking. When refrigerant leaks from a system it not only emits the refrigerant gas but some of the refrigerant oil as well. So if you look for signs of oil seepage you can spot a leak without having to grab a leak detector or black light. In this case the only oil residue was below the cycle switch at the dryer. It looked like a small leak so I expected to find the system with a low charge but not empty. I connected the low pressure side to the recovery machine and did indeed have some refrigerant pressure. 

Now with that pressure reading you can tell there is enough refrigerant in the system that the compressor should be able to engage. You can't tell if how much refrigerant is in there. If the system is low and the compressor is engaged then the low side should be lower than you would normally expect to see on a fully charged system. When I turned the A/C on, the low side did go lower than normal and the suction hose was only cooling at 58F. Which was only slightly below room temperature in the shop at the time. 

We know the system is low but can't do a proper charge without knowing just how much refrigerant is in there so the next step is to connect the high side as well to the recovery machine and recover the system charge. 

The recovered refrigerant is weighed and reported by the recovery machine. A full charge is 2lb, we recovered 1lb 5oz. Also, like with a leak, some oil is recovered along with the refrigerant. The oil is separated into a bottle and measured so you can see how much to add on the charge. 

 This was a good time to change that cycle switch. 

Next up, evacuate to remove air and moisture followed by a system charge. 

Now it is pulling down to 39F.

On to the next job.

Kenny@GGAuto.Repair

Battery Keeps Going Down Update

 The 2013 Silverado testing showed good battery, alternator and no excessive draw so I had decided to look at a full scan for clues. 

The ground at G302 looked like a good place to inspect after I monitored the voltage at the passenger presence module and found it to be dropping to 8 volts during a crank. Looking under the passenger seat I found several loose tools stored there. The socket set was in a case but screwdrivers and crescent wrenches all were laid loosely. Both screwdrivers had worn into the wire harness. I removed the tools and placed them in bag. I put the tools in the passenger rear floor (extended cab). I cleared the codes and monitored the voltage for several starts and now the drop was  to 10.5 volts during cranking which should be fine. I did not access the ground which would require seat removal as it seems fine now. No codes have reset. 

Now did the "fix" address the battery complaint? I don't know. It will be a wait and see but I do seem to have taken care of the problem I did find. 

Kenny@GGAuto.Repair

"Battery Keeps Going Down"

 I had three of these "battery loses power" jobs to look at today. I enjoy electrical work. It usually can be done in a logical process vs mechanical problems which can be anything. <grin> Typically on an electrical system diagnosis you will start at the battery. You need a good and fully charged battery for tests to be relevant. It isn't good enough to just assume it is fine. You test. I like to test the battery by first disconnecting it from the questionable system so that there is no interference. Before disconnecting the battery on the 2002 Avalanche I connected a memory saver to the system which is a sort of portable auxillary battery that will keep the truck's system memories intact while I test the battery. 

The battery was good but would need a full charge. I like to use low amperage and slow charging because it is the most stable and reliable but it does take a few hours. 

Once the battery was fully charged and cables reconnected, I removed the memory saver. Because the truck system never lost a power source I didn't have to wait for the system to enter sleep mode, it was already there. I could immediately test both the main circuits feeding from the ground side and found current draw well within acceptable range. 

I also found the alternator to be working properly. 

So, the battery was good, alternator good and no excessive draw on the battery. What was the problem? When I was disconnecting the battery terminals I had noticed the ground cable was not fully tight and it would not tighten when I did try the bolt. I went ahead and disconnected for the testing but once I was reconnecting the battery I could see the ground bolt was stripped. A new bolt tightened fully and I had a good connection. So what I found bad was a ground terminal connection at the battery due to a stripped bolt. 

Next up was the 2001 Crown Vic. The battery was completely drained on it and it was a new battery. I had to disconnect the battery from the car to even get it to begin charging so I knew this one had excessive draw. Once I was able to test current draw on this one, I could see why the battery was dead. 

Instead of starting by isolating circuits I thought that just might be something I could see on, like a trunk light or glove box light or something. I noticed a glow inside and there was something connected to the power outlet inside the car and the connector led was lit up. It was an aftermarket seat warmer on the passenger seat. The switch of the warmer had 3 settings but all were drawing power. I disconnected the warmer and all was good. 

Now the 2013 Silverado battery was up to 90% so didn't take long to reach full charge. Alternator tests good and all three of the main circuit feeds from positive post have draw within specs. 

Not sure what I'll find there but at least gonna let it sit overnight. It isn't unheard of for a computer to suddenly wake up on occasion and turn a few things on that shouldn't be. Gonna do a full system scan for clues and see what it does overnight. 

Kenny@GGAuto.Repair