2004 Chevrolet Silverado 4.3, Left Side Marker/Turn Signal Bulb Replacement

(This is not a picture of the actual vehicle we worked on. This is a similar vehicle, a 2004 Silverado. The picture is from: http://www.edmunds.com/chevrolet/silverado-1500/2004/?sub=regular-cab.)

We did an oil service on a 2004 Chevrolet Silverado 4.3. As part of an oil service, we always do a safety inspection on the vehicle. The safety inspection consists of checking things like tire pressure, belts and hoses and the external lights, among other things.

As we checked this one, we found the left side marker/turn signal bulb was not lighting. Many have questions about how to change certain bulbs on vehicles. Some are easier than others. Here is how you change this one. 

First, we had to remove the headlamp assembly. To do this, we had to remove the holding pin. It simply slides out.

Once the pin is removed, the headlamp can be lifted up and moved out of the way. We did not disconnect the headlamp, we just simply moved it aside to gain access to the lower assembly.

Now that the headlamp assembly is moved, we can get to the lower assembly. There is a plastic tab that moved be pressed to snap the assembly out of the bracket, allowing it to be moved to get to the bulb. In the picture below, I am pointing to this plastic tab with my screwdriver.

Once the tab is pressed, gently pull forward on the assembly. Be careful as this is done, so as not to break the plastic tabs. The picture below shows the assembly moved out from the bracket.

Below is another picture of me pointing to this plastic tab, this time with the assembly removed. This gives a better view of the tab.

At this point, it is a matter of replacing the burnt bulb. A simple twist of the connector will free it from the housing, then pull the old bulb out and replace it with a new one. The next picture shows the bulb now illuminated.

We then put the connector back into the housing and snapped the assembly back in place.

When reinstalling the headlamp assembly, you must get the plastic tabs/line up pins in the proper slots. The picture below shows the two tabs on the bottom of the headlamp assembly.

Those two tabs go into two slots. The picture below shows the two slots.

Once these are lined up properly, the headlamp assembly will go back in place and the holding pin can be slid back into place.

Once everything was back together, we did a quick recheck to make sure the bulb was illuminating properly. 

2000 Chevy Astro, 4.3, Crank/No Start Condition (Fuel Pump Voltage Drop Testing)

This 2000 Chevrolet Astro 4.3 came into the shop with a customer concern of a crank but no start condition. The customer had been driving the vehicle, went to start it again and it would not start.

I determined the fuel pump was the culprit. It was an intermittent issue, the fuel pump would prime and function some of the time, but mostly it would not. I knew we would need to replace the fuel pump, but I wanted to do some checks before we did.

It is important to check the circuitry of the fuel pump to be sure everything is okay there. It is a common mistake for a person or shop to simply replace the pump without checking the circuits. Often times, this causes comebacks or a recurrence of the same issue not long down the road.

One of the tests I do, is to perform a voltage drop test on the power (feed) circuit and on the ground circuit. A voltage drop is an invaluable test to confirm the integrity of the circuitry.

To perform a voltage drop test on a fuel pump, you need jumper wires and a DVOM. You also need the circuit "loaded" to do a proper test. In this case, that means you want the fuel pump engaged or priming, and checking the values when the component is under a load.

First, I checked the power side of the circuit. I backprobed in at the power wire for the pump (you will need a wiring schematic to determine which wire this is) and attached my probe to the positive terminal at the battery. With key off and the fuel pump not primed we see battery voltage on this circuit. (The voltage was a bit low, due to cranking to get the intermittent problem to occur.)

When we turned the key on and the fuel pump primed we saw what our voltage drop was.

(Sorry for the glare.) The reading on the meter is .534 volts, or basically, half a volt. The general rule for a voltage drop test of this kind is you do not want it to exceed about .5v (1/2 a volt). Here with our reading, everything is okay. We don't want to be too dogmatic about the .5v rule. As long as it is relatively close, it is fine. Typically a bad reading will be overly excessive, say 3-4 volts.

Next, I wanted to do the same test, but this time on the ground circuit. I backprobed the ground wire for the fuel pump and but my lead to the negative battery terminal. With key off, pump not primed we are reading 0v., which is what we expect for a ground.

We then turned the key on, with the fuel pump primed and read the voltage drop reading.

(Again, sorry for the glare.) You can see we are well under our .5v limit. We are below .1v, so no problem on this circuit either.

At this point, there was nothing left to do but to replace the pump. We inspected the gas tank for any contaminants and made sure the gas and tank were nice and clean. After replacement, we tested it and drove the vehicle. Everything was now fine.

We also changed the fuel filter, which was extremely clogged. It  probably contributed to the failing of the pump. We also put some good injector cleaner through as well.

2002 Chevrolet Cavalier 2.2, Engine Light on with a P0440 Code Stored

This 2002 Chevrolet Cavalier 2.2 came into the shop with a DTC P0440 Evap Emissions System Fault.  The first thing we did was to give a visual inspection of the EVAP system.

We did not see any obvious problems, such as, broken or disconnected hoses, unplugged components (i.e. purge or vent solenoid), broken wires, or loose/missing gas cap.

Many people, when presented with this code, will automatically replace the gas cap.  While these caps do need replacing from time to time for maintenance issues, this may not solve the problem.  In this case, the gas cap was not the issue.

We then decided to use our diagnostic tool and, using its bi-directional command capability, commanded the purge and vent solenoids on and off.  When we did, we heard (and could feel) each one turning on and off as we commanded it.  We did this several times to ensure there was not an intermittent problem with sticking in the solenoid.

Next, we connected our smoke machine, which we use to check for EVAP leaks.  Again, using the diagnostic tool, we commanded the vent solenoid on (which closes the valve . . . this valve is normally off and thus open, to do the test it must be "On", meaning the vent is closed, so as to allow the system to hold the smoke in), and tested the system with smoke.

The picture below shows the evidence.  It is a bit hard to see, so we have drawn an arrow to point to the evidence.  What we saw was smoke boiling out of the vent solenoid, even though we were commanding it "On", thus closing the vent.  Therefore, with the vent "On" no smoke should have been escaping.

With this evidence, we removed the vent solenoid.  What we found is that someone had tie-strapped the diaphragm.  More than likely, a previous owner (our customer said they had not done this) knew about the problem and tried to rig it to work.  Not a good idea.  The solenoid was actually leaking from around its diaphragm, so a new one was in order.  A picture of the old one, tie-strap still on is below.

The next picture shows the new vent solenoid in place.

  
Just FYI, there is a short wiring harness (see below) connected to the vent solenoid.  These are notorious for fraying and breaking, due to rear end movement.  Like the gas cap above, this was not the cause of this failure.  Silver bullet fixes usually end up costing a customer far more money than simply taking it in to a professional to have it properly diagnosed and repaired.

Here is the short wiring harness (I am pointing to it in the picture).

After completing the repair, we cleared the codes and data associated with it.  We then ran a EVAP system test with our smoke machine.  The test passed.  A picture of that is below.  You will notice the green lit LED indicating the test completed and passed.

There are many variables when it comes to diagnosing and repairing an EVAP system.  A basic understanding of how the EVAP system works on that particular make and model is essential.  A visual inspection is always the first place to start.

Don't jump at silver bullet fixes.  You may get lucky and it may be your problem and repair your vehicle.  Then again, you may spend quite a bit of money chasing several silver bullets and in the end be left with the original problem.

When in doubt, find a professional you can trust and take it to him/her and let them do the proper diagnostics and repairs.  It may end up saving you far more money in the long run.

I know the economy has been rough and times are tough.  But, throwing parts at a problem can compound that problem quickly.

2007 Chevrolet Colorado LT 3.7 2WD, P0128 Code

Just FYI, the Colorado pictured above is not the one this issue occured.  I did not take a picture of it, but I thought this one (another customer's) would do.

This vehicle came in with a customer complaint of the CEL being illuminated.  I ran the codes and discovered it had a P0128 DTC.  P0128 is a Coolant Thermostat code.  However, some tests need to be performed before relacing a thermostat.

I first performed tests on ECT and its wiring.  Everything checked out okay.

I then started the vehicle and let it idle for several minutes, long enough to reach normal operating temperature.  Below you will notice the temp hand has hardly moved even though the truck had been idling for several minutes.

I then connected my diagnostic tool to see what temp the sensor was showing.  Again, as with the temp hand, it was woefully low.  Sorry for the glare, but the temp is reading only 140 degrees. 

After taking it for a short drive, the temp remained very low.  It only got as high as 150 degrees.  Obviously, there is a problem in the coolant system not allowing the vehicle to reach normal operating temperature.

After gathering the evidence, I decided it was time to take a look at the thermostat.  To easily reach the thermostat on these vehicles, raise the vehicle and go through the driver's side wheel well.

After removing the left tire, the inner fender trim has to be removed. 

Here it is on the floor.  It has six retainers holding it on.

Now, the thermostat housing can be observed.

In order to drain the coolant on this vehicle, the lower radiator hose must be removed from the radiator.  There is no drain plug on these models.  It can be a bit messy, but not too difficult.  In the picture above, you can see the lower hose connected to the thermostat housing.

There are two 10 mm. bolts holding the housing on.  Below is the entire assembly (lower hose still attached).  On these models the thermostat, housing, and gaskets come as one assembly.

Upon inspecting the thermostat it was obvious what the problem was.  Notice below (I'm pointing to it) that the gasket has come out of place.

This was allowing coolant to bypass through the opening.  As a result, the thermostat was partially open and not allowing pressure to build in the system or allow the coolant to reach normal operating temp.

Once the new one was installed and the coolant was at full, the temp hand at idle came up as it is suppose to do.  The difference in temp can be seen below on the scan data.

Now the temp is reading around 200 degrees.  This is where it should be based on the amount of time it was idling. 

A quick test drive and check for leaks and a recheck of coolant level (after the vehicle had cooled) and the repair was verified.

2004 Chevrolet Colorado 3.5 Gas Smell From Vents

Had this 2004 Chevy Colorado come into the shop with a customer complaint of smelling raw gas fumes when he had his heater running.  He was worried gas was somehow entering into his vent system.

First step was to raise the hood and inspect for any leaking fuel components under the hood.  I had in mind a possible leaking injector, but instead found a leaking fuel pressure regulator, as you will see below.  You will notice the wet spot on the regulator where it had been leaking.

I replaced the faulty regulator with a new one.  There are a couple of torx bolts to remove along with the regulator from the fuel rail and a fuel line.  There are two o-rings that have to be replaced as well.

Finished the repair and no more raw gas smell coming from the HVAC vents.

1998 Chevrolet S10 2.2, Brake Lights Not Working

This vehicle came into the shop with a customer concern of no working brake lights.  The vehicle had been taken to another repair shop a few weeks ago and the customer was told it would cost several hundred dollars to repair the problem.

I confirmed that all three brake lights were inoperative.  This model has the customary two brake lights on the rear and a brake light called the Center High Mount Stop Light, or CHMSL for short.  All three brake lights were inoperative. (After doing some further investigation after I repaired the truck, I found the CHMSL bulbs were blown.)

This led me to a quick look at a wiring diagram, which led me to take a look at the Underhood Fuse Panel.

When I removed the cover something caught my eye, even before I could check any fuses.  I noticed something was missing.  Where I am pointing you will notice four empty cavities.  This is where the CHMSL Relay is suppose to be . . .  but it's not!  The relay would look like the relay above my finger (the grey rectangle).

I happened to have one in the shop.  I plugged it in.  Below I am pointing to the now present CHMSL Relay.

Sure enough, with a quick test of the brake pedal . . . presto!  the brake lights were working.

This is a quick post just to remind us not to overlook the small things.  Before pulling out the PowerProbe or Test light or whatever else, be sure to give a visual inspection of the components.  As this job reminds us, first make sure they are where they are suppose to be; and second, make sure they are in good/working condition.

Sometimes the easy, simple solution is the right one.

2001 Chevrolet Impala LS 3.8, Intermittent Stall

This Impala came into the shop with a customer concern of an intermittent stall.  Customer stated it had happened 2-3 times.  It had happened when the customer was coming to a stop and once in a drive-thru lane.

The customer said the CEL (Check Engine Light) was on, but that it had been so for over a year. 

First things first, I connected my diagnostic machine and checked for any present DTC's (Diagnostic Trouble Codes).  The vehicle, as implied by the customer, had many stored codes.  The one that caught my eye in reference to the current complaint was a P0102 MAF (Mass Air Flow) Circuit Signal Low.

Now time to get to the MAF sensor.  When you look under the hood you will see a cover over the engine.

To remove this cover, twist the oil fill neck counter-clockwise and it will pull out.

I then removed the cover.

With the cover removed from the vehicle the MAF sensor is in plain view.

 

 

I started the vehicle and saw there was definitely a problem with the MAF sensor based on the info on my diagnostic scantool.

My main attention, per the DTC, was the signal wire on the MAF. I decided to check the waveform and see what it looked like. The wave form should be nice and squared. You can see from the photo below this signal was not!

 

 

It was obviously time to replace this faulty MAF sensor.

 

In order to remove the MAF sensor, you need a T20 Anti-Theft/Security Torx Bit socket.  There are two screws holding the sensor in place.  Here is a look at the sensor removed.

 





Now to check the waveform on the new MAF sensor.  The waveform now looked normal.  This verified the diagnosis and the repair.

I then cleared the codes and took the vehicle for a test drive or two.  I also allowed it to sit and idle.  The P0102 did not come back.  I informed the customer of the need to do further repairs in relation to the other DTC's.