Air Care News
January 2001
Tricky Chevy took real detective work
by Doug Decker
We recently had a customer at the Denver Emissions Technical
Center who was wrapping up an engine swap and was struggling to isolate emissions and driveability
problems. The vehicle was a 1989 Chevrolet S-10 and the engine was a 1993 LT-1 Chevy 350 SFI with
a 700R4 automatic. The installation was very clean and well done with an aftermarket wiring harness
and aftermarket PROM chip in the V-8's computer.
This hot rod had failed for CO at 197 grams and was low on power.
It came to the technical center for an engine change and CO diagnostic evaluation. We went underhood
with the DVOM, back probing the O2 sensor connector and came up with about 0.75
volts -- a rich signal. We hooked up the scan tool and right away noticed a rich command to the injectors,
but -- 0.45 v bias voltage on the O2 sensor signals. Why the difference of 0.3v,
and more importantly, why a rich signal and a rich command?
Now it was time to really start thinking about this problem.
If the bias voltage feed from the PCM is high, maybe we have a bad PCM or PROM. Normally you'd
expect a slightly rich bias from a performance PROM, but not to this extent. We're always a little
wary of aftermarket parts, and the owner still had the OEM PROM for the PCM, so we reinstalled it.
Our wariness was unfounded; there was no change. We advised the owner that he likely had a faulty
PCM and replacement appeared to be the proper repair. He left us in budget shock and we weren't
satisfied either. There was that nagging feeling that we'd overlooked something.
In one of those 4 a.m., out-of-a-sound-sleep moments of
insight, the lost 0.3 volts came back: "If it’s not on the power side, it must be on
the ground side!" However, we’d verified voltage drop from the PCM to the body as being
less than 0.05 volts. First thing in the morning we had the vehicle owner back in the shop.
Recalling the textbook method of doing voltage drops, we went
in search of the lost 0.3 volts on the ground side. Using the DVOM negative lead on the battery
negative post (not on the cable clamp) and positive lead on the ground pin of the PCM (you’ll need an
extension lead to get inside the cab) with the circuit connected and energized, viola,
0.3 volts -- a bad ground. The next step was to work through each connection in the circuit
– not too tough on an automotive ground circuit because the body acts as the ground. With the circuit
still connected and energized, we checked from the battery post to the clamp, clamp to the cable, cable
to the engine block, engine block to the O2 sensor bodies. All were still below 0.05
volts. This was a double- or split-battery ground cable, with the smaller wire being the chassis ground,
so we repeated the textbook process, checking battery clamp to chassis wire, chassis wire to the chassis,
etc. -- still all were well below 0.05 volts. So, where was the 0.3 volts?
The PCM was mounted inside the cab and the voltage drop from
the PCM ground to the sheet metal of the cab was ok, but the cab was mounted to the chassis on brand
new rubber mounts! A quick voltage drop check between the chassis and the cab sheet metal
uncovered the missing 0.3 volts. The cab was partially insulated from the rest of the vehicle.
A fat #8 jumper from the engine block to the firewall and we were back in business. A final recheck of
the voltage drop from the battery post to the PCM ground pin showed less than 0.05v.
The truck headed off to the emissions station but was back
all too soon. Although it ran pretty well, it was still failing at 46 grams CO. We hadn’t verified
that it was in fuel control, and it wasn’t. Plugging the scan tool back in, we found that block
learn (fuel trim) for the left bank O2 sensor was at 104 (very low) and for the right
bank it was 151 (very high). Thinking that we might have a bad injector or a bad O2
sensor, the owner volunteered to swap banks of injectors (no change) and then swap O2
sensors bank for bank, again with no change. With one technician watching the scan tool, another technician
went underneath and disconnected the left bank O2 sensor. Curiously, the block learn
for the right bank started to creep back down! Reconnecting the left, we disconnected the right
O2 and the block learn for the left bank started creeping back up.
Guess what? The wiring harness manufacturer had swapped
positions for the left and right O2 sensor connectors!
In order to make this harness right, we had to untape it
and correct the wires’ positions, reconnect the O2s correctly and then retape them
in place. (We could have swapped pins at the PCM connector, but the color codes would have been wrong).
As soon as the O2 sensors were properly connected, the engine smoothed out and
purred like a kitten. Fuel control was verified and the block learn for both banks came in at 126 to 128 –
right on the money. The truck tested and passed at 14 grams CO – not the best, but the owner assured us
that he would get the catalysts good and hot in the coming weeks, which would further clean up the
emissions. It seems our wariness of aftermarket parts – in this case the wiring harness – were well founded
after all.
The real lesson on this truck was not the harness, but that for
finding circuit faults, a proper voltage drop test procedure cannot be beat. The voltage drop test we
did as described above found the lost 0.3 volts in less than ten minutes, and the repair took less than
that – with no parts cost. Don’t rely on an ohmmeter – it will lie to you because the system (circuit)
is not under load. Learn and use the proper voltage drop procedure – it will not let you down.
Fix the problem – not the symptoms!
NOTE: Strictly speaking, engine changes are a violation of federal emissions tampering laws, if
a professional shop for hire performs them. The Air Care Colorado Program has always realized that people
are going to change engines; and this swap was performed by the owner on his own vehicle. Our policy states
that any vehicle with an engine change will be inspected according to the model year of the body/chassis
(as titled) or the engine configuration, whichever is newer. This applies to the tailpipe emissions
limits as well as the visual inspection for emissions equipment. Contact your Emissions Technical Center
for more information on engine change policies.
Doug Decker is an environmental protection
specialist at the Colorado Department of Public Health and Environment.
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Being a registered
repair facility is great advertising --
especially if VRFs are correctly filled out and returned
by Renee Allen
Mike Knarr, the program's new Repair Industry Coordinator, confirms what
many registered repair facilities already know -- it's great advertising to be one. Simply by
becoming a registered emissions repair facility, the shop is listed in the
Emissions Repair Guide, a booklet that helps vehicle
owners choose a qualified repair shop when their vehicle fails an emissions test. "It's like a mini Yellow
Pages," says Mike.
Currently, 631 repair shops (that's about one third of all
repair shops in the metro area) are listed in the REI Guide. However, there is more to it than just
being listed. Where a shop is listed is key. "Like any advertising, the higher you are on
the list, the better your chances of getting more business," Mike says.
Top listing is optimal for a number of reasons. Besides being
the first name people see, it also means that the shop is good at what they do -- what the people are
looking for -- emissions repairs.
A facility's placement in the Guide is based on a
shop's rating. The higher a shop's repair effectiveness (REI) score,
the more success it has had in repairing emissions-related failures the first time. The most successful
shops earn the highest placement in the Guide. Ratings are calculated using emissions repair
data. Elements used to calculate these ratings are:
 number of
vehicles repaired and tested
number of vehicles that passed first retest
number of multiple tests
number of waivers issued to vehicles worked
on by that facility
The highest possible score is 100. This means the repair
shop repaired every vehicle brought to it and each vehicle passed on the first retest.
But hold on, just doing the repairs does not guarantee a good
ranking; the Vehicle Repair Form (VRF) must be returned with the vehicle at the time of the second
test. Without a VRF there is no way for a shop to get credit for repairs.
In order to get credit, a shop must fill
out the VRF as completely as possible. Most importantly, the VRF must contain the following
information:
shop phone number
shop name
shop number
With this information the repair can be entered into the repair
database. If this information is not available, illegible or incomplete, it could hurt the shop's
ranking in the Emissions Repair Guide. For example,
if a shop is doing repairs but none are being recorded, it runs the risk of being rated "inactive"
(indicated by double asterisks) or as not having done enough repairs to be rated (indicated by a single
asterisk) and placed at the bottom of the list with no score. Another scenario is that the customer
who obtained the repair and takes the vehicle back for the second test does not return the filled out
VRF. To avoid this, many shops take repaired vehicles for a retest as a customer service, thereby
ensuring their repairs are counted.
Make sure you are getting credit for those amazing repairs you and
your techs are pumping out. Make sure the VRFs are returned to the inspector at position one of the
testing station with the registered repair facility number, name and phone number written legibly on the
VRF. "It's better for shops to bring cars back in for the retest so they can make sure they obtain
credit for their repairs," Mike says. "It closes the loop of relying on a customer to
return the VRF."
So, how do you get a high rating and subsequently a high
placement in the REI Guide? Simple -- perform excellent repairs and get credit!
Renée Allen is a public relations
specialist with Envirotest Systems Corp.
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In the last several months of the
"Top Tech" program, the following technicians have been honored for
their excellent emissions repairs. Congratulations to these "Top Techs"!
Rodney Scohy
Rodney is a second-time winner, having also won the Top Tech
award back in July 2000. He is an ASE master technician who specializes in emissions-related diagnosis
and repair. He has been repairing cars for over 20 years and has worked at Rodine’s for the last eight.
Derek
Latham
Derek has been an automotive tech for more than 10 years and has been at Seyfer’s
Automotive for more than 11 years. (He started at the front counter writing service!) He is ASE certified
with L-1 and the new X-1 cert. His training includes FIRST & EDGE and he
likes the challenge of those hard-to-fix driveability and emissions failures.
Terry Madigan
Terry is an ASE certified technician, including L-1. He has
at least 25 years experience as a technician, with 21 of those years working at Tapp’s Auto Service. Terry
has completed both FIRST (Fundamental Inspection and Repair System Training), and EDGE (Emissions
Diagnostic Graduate Education), and his specialties include emissions, driveability and electronics
diagnostics and repairs.
Submit paperwork for Top Techs to: Dave Moreau, CDPHE APCD-MS-B1, 4300
Cherry Creek Drive South, Denver, CO 80524-1530 or fax - Attn: Dave Moreau (303) 782-5693.
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Fooling the system
doesn't fly with DOR techs
by Tom Myrsiades
The Colorado emissions program has a provision allowing a vehicle
owner to obtain a waiver if their vehicle continues
to fail the emissions test after the owner has spent $450 in emissions-related repairs. The vehicle
owner may call the Department of Revenue Emissions Office and request a waiver. The information received
from the consumer is assigned to a field technician for an appointment to verify the repairs and issue the
waiver. All repairs must be verified and approved by a Department of Revenue technician prior to issuing
a waiver. The approval rate at this time is approximately 55 percent of all waivers requested. Recently,
our office processed a waiver request and an appointment was set with the customer to bring their vehicle
to a test facility.
In this case, our customer provided the DOR's Tim Barnett with a
repair order receipt indicating both cylinder heads, an O2 sensor, distributor cap,
rotor and spark plug wires had been replaced for a total of $683.00 for parts and labor. This documentation
would qualify the vehicle for a waiver providing the repairs were confirmed. Tim's evaluation of this
vehicle revealed none of the above-mentioned parts or
repairs were completed on this vehicle. Additionally, this vehicle smoked severely at all speeds and the
catalytic converter was missing. The waiver was denied and the customer was advised of the deficiencies.
Our ensuing investigation revealed that the customer and an unethical
repair shop assumed all they had to do was come up with a repair order indicating the appropriate repairs
had been completed and a waiver would automatically be issued. Notices of violation were issued to the
station involved, for passing the catalytic converter, and the district attorney's office was notified
concerning the repair shop.
Please pass the word around. This kind of fraud will never fly as
long as technicians like Tim Barnett are out there doing their jobs. If you notice a similar situation,
please contact the DOR at 303-205-5603. For technical questions concerning emissions repairs, contact the
Department of Public Health and Environment's Technical Center at 303-744-2442.
Tom Myrsiades is an emissions supervisor with the
Department of Revenue.
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