NO HEAT THROUGH VENTS & OBD SYSTEM QUESTION

[EileenLaf]

Hi....hope the New Year's been good to everyone so far. Before taking my 1998 ETC for diagnosis & repair, I’m hoping to get opinions and/or ideas as to what might be wrong with my heat (trying to avoid unnecessary repairs & costs, too). Seems like it might be HVAC Blower Motor, but wondering if it could be as minor as a module or sensor.

NO HEAT BLOWING THROUGH VENTS

Heat doesn't blow from any vents (no defrost, either); however, if I put my hand up to the vent I can feel heat. While driving around town, minimal heat blows from vents & when completely stopped, nothing blows out vents. If I’m driving between 80 mph & 90 mph heat blows from vents as it should. During Summer & Fall the A/C & A/C Off (fresh air) settings worked fine with air blowing through vents. It was only when 1st using the heat that this problem started; of course, the timing could be coincidental.

I entered Diagnostic Mode & the Set Codes were as follows:

1. SDM - B1327 H
2. MSM - B2118 C (What exactly is a Front Vertical Sensor?)

If the HVAC Blower Motor has malfunctioned, should it set a trouble/diagnostic code? If yes but a code won't set, what could be the reason for it?

OBD SYSTEM QUESTION

I read that the SES light will come on & stay on when a constant malfunction is detected. The car's SES bulb check performs as it should; however, I've never experienced a time when the SES light has stayed on when necessary. For instance, the above-referenced code, MSM B2118 C, has never triggered the SES light to come on, let alone remain on. I've had prior malfunctions for which DTCs would’ve been set, thereby triggering the SES light to stay on, but it hasn't. DIC Messages and/or abnormal operation of my car have alerted me to prior troubles.

Any idea(s) as to why the SES light wouldn’t work as intended/expected with constant malfunctions? Is it possible my OBD System isn’t properly working? If so, what could be the cause?

As always, I greatly appreciate everyone's time and assistance when responding to my questions. Thanks and if additional info is needed please let me know.....I’ll respond ASAP.

[Logan]

The SES lamp is really a federal requirement for a powertrain malfunction that would cause a change in the emissions. Its not really there to flag a malfunction of any system on the vehicle.

There can and are powertrain codes that will not even turn on the SES. There are type A and type B codes for example.

There has to be code written for the PCM to detect a problem correctly. There is code for something like a p0300 misfire. There is not code to detect a loose engine ground.

All of this is to be in Federal compliance with the vehicle emission system.

As for the HVAC blower. On your car..the blower motor uses a internal module...it is replaced as a complete blower motor unit. They can and do go bad. I would not call it a common problem...but rather a known problem. Spark plug wires resting on the blower motor can also kill it.

[Cadillac Jim]

B1327 Vehicle system voltage below 9.0 volts HISTORY
B2118 Front Vertical Sensor Failed CURRENT

The B1327 is thrown if the battery voltage drops below 9.0 Volts when starting the car. This can happen if the battery is down, say from the car not being driven for a couple of weeks, and the dip in battery voltage when loaded by the starter motor. It can also be bad battery cable connections or a mark of a dying battery, but with no other codes it probably is a one-time thing and you can forget it, so long as you now have a fully charged battery.

The B2118 is the position sensor for the electric sensor for the height of the front of the driver's seat. It is used by memory seats to save and restore power seat settings when fob 1 and fob 2 are used to unlock the car. Sometimes the position sensors can throw a code if a power seat setting is pushed all the way to a stop. The fact that it remains CURRENT may mean that the seat is set with the front all the way up, or that indeed the front height sensor has gone bad.

A bad blower motor may not throw a code because it;s on its own module that is not on the car's network and thus isn't part of the OBD system. The way to test it is to apply power and ground, then to put either 12 Volts or ground to the signal terminal, I forget which. If it doesn't blow, the module is bad. The newer ones (i.e. replacements) are better protected from plug wires and are a little different form the originals. Be careful and follow the instructions well if you replace it yourself.

[EileenLaf]

The SES lamp is really a federal requirement for a powertrain malfunction that would cause a change in the emissions. Its not really there to flag a malfunction of any system on the vehicle.

There can and are powertrain codes that will not even turn on the SES. There are type A and type B codes for example.

There has to be code written for the PCM to detect a problem correctly. There is code for something like a p0300 misfire. There is not code to detect a loose engine ground.

All of this is to be in Federal compliance with the vehicle emission system.

As for the HVAC blower. On your car..the blower motor uses a internal module...it is replaced as a complete blower motor unit. They can and do go bad. I would not call it a common problem...but rather a known problem. Spark plug wires resting on the blower motor can also kill it.

Thanks for your reply......after posting my questions I found info relating to the SES & how it's supposed to work. Prior to the info I found & your reply I didn't realize the SES will only stay on for specific codes. I appreciate the help.

[EileenLaf]

B1327 Vehicle system voltage below 9.0 volts HISTORY

B2118 Front Vertical Sensor Failed CURRENT

The B1327 is thrown if the battery voltage drops below 9.0 Volts when starting the car. This can happen if the battery is down, say from the car not being driven for a couple of weeks, and the dip in battery voltage when loaded by the starter motor. It can also be bad battery cable connections or a mark of a dying battery, but with no other codes it probably is a one-time thing and you can forget it, so long as you now have a fully charged battery.

The B2118 is the position sensor for the electric sensor for the height of the front of the driver's seat. It is used by memory seats to save and restore power seat settings when fob 1 and fob 2 are used to unlock the car. Sometimes the position sensors can throw a code if a power seat setting is pushed all the way to a stop. The fact that it remains CURRENT may mean that the seat is set with the front all the way up, or that indeed the front height sensor has gone bad.

A bad blower motor may not throw a code because it;s on its own module that is not on the car's network and thus isn't part of the OBD system. The way to test it is to apply power and ground, then to put either 12 Volts or ground to the signal terminal, I forget which. If it doesn't blow, the module is bad. The newer ones (i.e. replacements) are better protected from plug wires and are a little different form the originals. Be careful and follow the instructions well if you replace it yourself.

I did know B1327 resulted from my battery dying several times before replacing it. I went on BBB Industries website & found a TSB outlining exactly what you wrote about......problem with battery draining when car sits for a week or so & mine fell into that category.

As luck would have it, the day after my post, my car wouldn't start - dead battery AGAIN. This time it made no sense because I drove the car a day or 2 before & a new battery was installed July 2013. After charging the battery I entered diagnostic mode and got the following codes, all of which indicated "HISTORY":

1. IPC B1552 Keep Alive Memory (KAM) Error
2. IPC U1255 Class 2 Communication Malfunction (Serial Data Line Malfunction)
3. PZM B1552 Keep Alive Memory (KAM) Error
4. PZM B1558 BCM EPROM Checksum Error

This was the 1st time I've seen these codes after a dead battery; however, since none of the codes are current can they be disregarded now that the battery is charged? I'm still bothered by the fact that a 6 month old battery died, though.

I figured B2118 was related to the driver's seat but not specifically the height sensor - thank you for the info. I can pretty much bet that I pushed the setting all the way to a stop & will check to see if that's what threw the code.

With respect to the blower motor not throwing a code, I didn't realize until after posting my questions & reading both responses that the SES stays on only when specific DTCs are set. I'll definitely follow your test instructions. The new blower motor now comes with a heat shield, doesn't it? Is this what protects it from the plug wires?

Thanks so much for your detailed reply - it's most appreciated and extremely helpful. Interested in your thoughts on the "new" codes set after battery died & hoping they were set only as a result of the drained battery.

[Cadillac Jim]

The old blower motor came with a flexible shield that was installed with it. Apparently if a plug wire is laid on top of the blower motor for a long period of time, as it happens when a tech does not replace the plug wires in the looms or even cut them to length when replacing them, in time this can cause the module in the blower motor to blow. There was a redesign many years ago to address this.

You can clear the codes form the A/C buttons, too. I would clear them and see if any come back.