Case studies

  • Make of vehicle:

  • Symptoms:

  • Fuel type:

In this series a PicoScope automotive oscilloscope is used to diagnose vehicle faults. Fault-finding procedures, detailed explanations of components and systems, and high-performance automobiles make this high-octane series a must read.

Vehicle Case study Fuel All vehicles All symptoms All fuel types
Vehicle Case study Fuel All vehicles All symptoms All fuel types
Ferrari
360

Intermittent non-start
The car came in with an intermittent non-start complaint, but after quizzing the customer it became more of a “no crank” problem

Petrol Ferrari Intermittent non-start Petrol
Lotus
Elise II

High idle speed and cutting out
The vehicle came in with a complaint of high idling and occasional cutting out.

Petrol Lotus Cutting out,
Intermittent non-start,
Petrol
V8

Troubleshooting a knock sensor
The vehicle arrived with the engine MIL on but with no noticeable running problem. Checking the system with a scan tool, I found these diagnostic messages: Accelerator potentiometer, Knock sensor Cyl 1-2-7-8

Petrol V8 MIL on but no symptoms,
Petrol
Lotus

2004

Intermittent misfire
The vehicle had an intermittent misfire and the engine MIL was on. I found the engine misfiring constantly, with excessive smoke issuing from the tailpipe, so I left it running for a little while to get a feel of the problem and to scan the system for trouble codes.

Petrol Lotus Engine misfire (intermittent),
MIL on,
P0201,
Petrol
BMW
X5

Intermittent misfire
When the book-in came, I allocated more time than usual to this one...

Petrol BMW Engine misfire,
Engine misfire (intermittent),
Intermittent non-start,
P0205,
Petrol
Audi
A2
2002

Heavy steering
I’d visited this 2002 Audi A2 once before with an intermittent problem of the power steering going heavy. During testing I couldn’t get the car to fail, and checking the system with the scan tool found no DTCs logged either.

Petrol Audi Heavy steering,
Petrol
Audi
TT Quattro
2001

CAN Bus Fault
A 2001 Audi TT Quattro arrived in the workshop with a complaint from the customer of an intermittent ESP light. At first the fault was not obvious at all. We had heard that the ABS modules could be a common failure but I had to be sure before fitting.

Petrol Audi CAN Bus error,
Intermittent ESP light,
Petrol
Subaru
flat 4 port and direct injection, non-turbo
2012

Cylinder misfire
An intermittent issue of the engine warning light illuminating and fault code “P0302 Cylinder 2 misfire” detected.

Petrol Subaru Engine misfire (intermittent),
MIL on,
P0302,
Petrol
Unspecified

Low speed ABS fault
The vehicle came in with the complaint that the ABS could be felt working through the brake pedal at very low speeds. I carried out a short road test to verify the complaint and, sure enough, the ABS would cut in at very low speeds; in fact, just before the car came to a stop.

Unspecified Unspecified ABS fault,
Unspecified
Unspecified

Scan tool communication fault
The car had an intermittent drivability complaint, bogging down under acceleration with no MIL flagging. The customer insisted that it wasn’t just intermittent; it was very intermittent.

Unspecified Unspecified No OBD communication,
Poor acceleration,
Unspecified
Unspecified

Poor interior temperature control
The customer complained that the interior temperature would occasionally hang at one setting. He couldn’t say at which temperature this happened, just that sometimes it stopped working. I decided to investigate.

Unspecified Unspecified Poor interior temperature control,
Unspecified
Ford
Escort
1999

Cranking with no start
This car was a 1999 Ford Escort 4 cylinder 1.6 litre and had been bought from a reputable used car lot with no apparent problem. After a few weeks the car had an additional inventory of lowered springs, alloys, up-rated stereo, and two big holes in the rear parcel shelf ready for some speakers.

Petrol Ford Non-starter with cranking,
Petrol
Ferrari
355
1999

Surging at idle and poor running
This customer reported bad surging at idle when the vehicle was warm, general poor running, and repeat DTC logging of LH BANK FRONT O2 SENSOR and RH BANK FRONT O2 SENSOR.

Petrol Ferrari MIL on,
Petrol
Seat
Arosa
2004

Non-starter
This vehicle had found its way to a specialist diesel shop with a no-start complaint. The car began by occasionally cutting out, but progressively got worse and eventually turned into a complete no-start.

Diesel Seat Non-starter with cranking,
Diesel
Vauxhall
Astra
2001

Misfire under load
This Vauxhall Astra 1.6 had a misfire problem under load. The repair shop had diagnosed the coil pack as faulty and fitted a new unit with plugs, but this made no difference to the problem.

Petrol Vauxhall Engine misfire,
P0300,
Petrol
Vauxhall
Zafira
2000

EGR valve
The customer complaint was intermittent cutting out. This was eventually narrowed down to only stalling at junctions: how important is correct information?

Diesel Vauxhall Cutting out,
EGR fault,
Engine stalling,
Diesel
Vauxhall
Corsa
2004

Non-starter
This 2004 Corsa 1.2 arrived with dash and engine auxiliaries already stripped and its trims and covers in the boot. In fact the ECM was missing and had to be sourced from the previous repairer; so a good start.

Petrol Vauxhall MIL on,
Non-starter with cranking,
P1615,
P1616 ,
Petrol
BMW
X5

Battery drain
This BMW had a complaint of intermittent no start caused by the vehicle battery discharging. Sometimes it would last two weeks and other times only last two days. The battery had already been replaced, twice, and the alternator overhauled and given a clean bill of health.

Petrol BMW Battery drain,
Intermittent non-start,
Petrol
Fiat
Bravo
1999

Intermittent speedometer
The case was a 1999 Fiat Bravo 1.6L with a complaint of intermittent speedo operation. The speedo would read correctly up to cruise speeds then would suddenly drop to almost zero.

Petrol Fiat Intermittent speedometer,
Petrol
Fiat
Punto

Electronic Control Module (ECM) failure
This Fiat Punto 1.2Lsuddenly developed a misfire and never recovered. It was driven to the customer’s own local garage, where they carried out the usual checks, and was starting to look like the ECM had failed.

Petrol Fiat ECM failure,
Petrol
Peugeot
406
2001

Misfire
This Peugeot 406 came to me with a complaint of misfire, and had with it one of the most comprehensive shopping lists I’d seen...

Petrol Peugeot Engine misfire,
Petrol
Fiat
Ducato
2004

Poor starting
The vehicle was a Fiat Ducato 2004 2.8 JTD with a repetitive complaint of poor starting. The engine would crank at good speed but took a while before it eventually fired, and once started the vehicle drove fine.

Diesel Fiat Poor starting,
Diesel
Vauxhall
Corsa
1999

V6 Transplant
Ordinarily I wouldn’t have given this the time of day had it not been for an unusual recorded trace, which I felt would be interesting to share. The eventual cause of the fault was… you’ll have to see it to believe it.

Petrol Vauxhall Engine misfire,
Petrol
VW
Golf 1.9 TDI
2003

Variable nozzle turbine pressure control
I was fortunate enough recently to get hold of a WPS500X Pressure Transducer and looked forward to using it right away. It didn’t take long before I found a perfect excuse to switch it on: the Variable Nozzle Turbine (VNT) boost control.

Unspecified VW Unspecified
Unspecified

Diesel engine rebuild testing
The Michigan Army National Guard operates and maintains a very large fleet of heavy diesel equipment. It is imperative that this fleet be kept at a high level of readiness and reliability at all times.

Diesel Unspecified Diesel
Audi
S2

Intermittent and progressive failure to start
The car was brought to us on the back of a tow truck, the owner reported that after running faultlessly for some four months after a new distributor had been fitted, one morning, for no obvious reason, the car would not start.

Petrol Audi Intermittent non-start,
Non-starter,
Petrol
Alfa Romeo
Spider
1998

Misleading MIL
The vehicle arrived at the workshop because the MIL (Malfunction Indicator Lamp) was illuminated. The vehicle showed no other drivability issues.

Petrol Alfa Romeo MIL on but no symptoms,
P0300,
Petrol
VW
Golf

Misfire
This VW Golf (1.8, 20 valve, turbo, engine code AGU) was presented to me with the fault described as a misfire at 2000 rpm.

Petrol VW Engine misfire,
Petrol
BMW
5 Series
2000

Braking fault
A 2000 model year BMW 5 Series was brought to us with the ABS/ESP light illuminated, following unsuccessful diagnosis and repair elsewhere.

Petrol BMW ABS fault,
ESP fault,
MIL on,
Petrol
Vauxhall
Signum
2003

Misfire
A 2003 Vauxhall Signum arrived at the workshop with a slight misfire and general flatness under acceleration. A scan provided the code P0301 (Cylinder 1 Misfire Detected) and a quick inspection confirmed that the insulation had failed on the cylinder 1 coil area.

Petrol Vauxhall Engine misfire,
P0301,
P1191,
Petrol
Toyota
Avensis
2002

System too lean
A 2002 Toyota Avensis came in with the MIL on and two DTCs present: P0171 and P0174 System Too Lean on banks 1 and 2 respectively. On the first visit I was asked to clear the codes (it was a motor trader’s car!) which I did, with the suggestion that it would most likely return.

Petrol Toyota MIL on,
P0171,
P0174,
Petrol
Ford
Focus
2003

Hard to start from cold
I had a 2003 Ford Focus 1800 TDCI Duratorq come in with a hard start issue from cold. Once it was warm it would start great every time. No DTCs stored and live data showing good pressure generation.

Petrol Ford Poor starting,
Petrol
Audi
A6
2001

Battery discharge
Recently I was faced with a customer who had completely given up on the idea of her car ever being fixed. The lady owner of a 2001 Audi A6 1.8 Turbo, explained to me how she has always had problems with the battery discharging.

Petrol Audi Battery drain,
Petrol
Smart
ForTwo
2004

Misfire
This story concerns an employee of Pico Technology and their journey to the office. About one mile from work the owner of this 54,000 mile Smart Fortwo started to experience a very noticeable misfire.

Petrol Smart Engine misfire,
Engine stalling,
Petrol
Dodge
Ram
2003

Catalytic converter
Recently I had a 2003 Dodge Ram 4.7 litre V8 booked in with the MIL reporting a problem. With only OBD connectivity I managed to pull P0420 catalyst efficiency bank 1.

Petrol Dodge Heavy steering,
P0420,
Petrol
Skoda
Octavia

Crankshaft reluctor
This vehicle was recovered from another garage after having its engine rebuilt. It would start and then cut out.

Petrol Skoda Engine stalling,
Petrol
Audi
A8
2003

Injector fault
A 2003 Audi A8 was having a problem with rough running which in turn was causing the engine management light to illuminate.

LPG Audi Cutting out,
P0204,
P0300,
P0304,
P1130,
P1138,
LPG
Peugeot
406
2001

Low Power P0191 P1138 MIL
Intermittent faults are the bane of our lives in the garage. Recently though we were fortunate to have the scope set up whilst a problematic Peugeot faltered before our eyes, thankfully the scope was gathering data.

Diesel Peugeot MIL on,
P0191,
P1138,
Poor acceleration,
Diesel
BMW
M3
2003

Electrohydraulic gearbox control
Knowing when to say “No!” is something that we learn as we progress through the ranks in the motor repair business, but sometimes we still succumb to the urge to take on an interesting job. We recently had a 2003 BMW M3 drop in on us, with two warning lights displayed and the customer complaining that he kept losing his gears.

Petrol BMW P1717,
Petrol
Mercedes
W140 S-Class
1995

Intermittent misfire
The Mercedes W140 S-Class V8 engine had developed an intermittent misfiring fault. The misfiring could be observed during idle speed when the engine was warm – however it was not a serious issue. Within a month it became apparent that as the engine coolant temperature reached 60 °C, the ‘intermittent’ fault became permanent.

Petrol Mercedes Engine misfire,
Engine misfire (intermittent),
Petrol
Audi
S3
2001

Rough idle
In July of 2010, a 2001 Audi S3 came to us with idling problems. To our disadvantage, a garage had previously worked on the vehicle and cleared the ‘DTC’ (Diagnostic Trouble Code) information from the ECU.

Petrol Audi P0102,
P0133,
P1114,
P1137,
P1296,
Petrol
Ford
Explorer
2002

Intermittent misfire
This is the tale of a 2002 Ford Explorer with an idle quality complaint. According to the customer the idle would surge, especially when first started and would even stutter a bit when put into gear. As the engine warms up, the problem fades and is much less noticeable.

Petrol Ford Engine misfire (intermittent),
Poor idle,
Petrol
Proton
Impian

Intermittent non-start
A Proton Impian was suffering from intermittent starting problems, and the vehicle randomly cut out. This caused the engine warning light to illuminate.

Petrol Proton P0340,
Petrol
BMW
E46 318i
2000

Non-starter
The vehicle had been driven through a flooded area, and water had entered the block via the air intake. The car cut out with the engine flooded with water. The cold water entered the hot cylinder block, and caused it to crack due to thermal shock. The engine had been replaced, but could not be started.

Petrol BMW No OBD communication,
Non-starter,
Petrol
Ford US
Windstar
1996

Misfire
Technician and workshop owner Rich Barton of Iowa, USA, was shown a 1996 Ford Windstar minivan that ran well when cold, but misfired badly when warmed–up.

Petrol Ford US P0174,
P1537,
Petrol
Chrysler
Concord

Misfire
This Chrysler Concord (coil over plug system) came in with a cylinder–specific misfire problem. With some testing I found that the number 5 coil had no spark.

Petrol Chrysler Engine misfire,
Petrol
Hyundai
Porter
2006

Cold start problem
This car had a cold start problem, where the engine ran poorly and white smoke was apparent. The previous engineer had changed injectors and the actual engine head, however the problem still occurred.

Diesel Hyundai Poor starting,
Diesel
Audi
A6
2006

Engine cutting out
The car came to us from a transmission repair center. The problem was an occasional engine cut–out during cold cranking. It is difficult for technicians to investigate this particular problem due to it occurring during cold cranking.

Petrol Audi Engine stalling,
Poor starting,
Petrol
VW
Golf
2001

Rough running
The car came to me after the previous repairer had spent a week or so head–scratching and internet–searching.

Diesel VW P1248,
Diesel
Peugeot
206
2006

Misfire
When cold starting this car would misfire, but when warm it quickly cleared. No misfires occurred under normal driving conditions.

Petrol Peugeot Engine misfire,
Poor starting,
Petrol
VW
Bora
2002

Faulty air mass sensor
Strange engine behaviour between 1200 rpm and 3000 rpm. There was a little bit of engine knocking and some misfire — with black smoke coming out of the exhaust pipe. The engine had a fluctuating idle rpm — sometimes worse than others.

Diesel VW Engine misfire (intermittent),
Poor idle,
Diesel
BMW
Mini
2001

K–Bus diagnostics
The vehicle was left with me and I was able to put a diagnostic plan in place. The vehicle started and drove fine, the TPMS is a manual reset function and would not reset.

Petrol BMW Airbag light,
Tyre pressure monitor,
Petrol
Mercury
Sable
1991

Surging at idle
Engine generally idled okay until it was shifted out of Park, and then it started surging. Going back into Park did not return to a better idle and continued to surge.

Petrol Mercury Engine stalling,
P0326,
Poor idle,
Petrol
Rover
45
2004

Rover 45 with MIL on, P0170 Fault Code
This car came with the MIL (Malfunction Indicator Lamp) illuminated but no reports of any running issues. The first action was to read the PCM (powertrain control module) for the stored code(s). There was only one stored.

Petrol Rover MIL on but no symptoms,
P0170,
Petrol
BMW
325i E36
1991

Poor performance
I was presented with this 1991 6cyl E36 325i BMW which had an on-going problem for the last two years and it seemed repairable. The complaint was lack of power, hesitation and the occasional cutting out on acceleration once warm.

Petrol BMW Poor acceleration,
Power loss,
Petrol
Ford
S-Max
2010

Sudden power loss
I admit that the fix is probably quite obvious using the parts darts technique or best guess scenario, but I thought this particular job demonstrated the use of the WPS500 as an everyday aid to speed up the diagnostic process.

Diesel Ford Power loss,
Diesel
Jaguar
E-type
1961

Unstable idle speed
The vehicle in question was a 3.8 E-type straight 6 cylinder. Our customers concern was unstable idle speed, reluctance to rev, and horrendous backfiring with hesitation at wide open throttle (WOT [the default position for E-type drivers]).

Petrol Jaguar Poor acceleration,
Poor idle,
Petrol
Jeep
Compass
2007

Cylinder misfire
I had a customer's 2007 JEEP Compass , European Spec, fitted with the VW 2.0l TDi PD engine (code BLY). Unfortunately standard VAG software (e.g. VCDS) cannot communicate with this ECU (due to it being a JEEP).

Diesel Jeep Engine misfire,
Diesel
VW
Golf
2004

Noise, Vibration and Harshness
A MK5 VW Golf 2.0 TDI with a distinct vibration throughout the cabin at a very specific road speed range of 67- 73 mph, presented a real nuisance at cruising speed. This problem resulted in the customer driving at 65 or 75 mph to avoid the vibration.

Diesel VW Cabin vibrations,
NVH,
Diesel
DAF
XF95

EBS braking fault
The customer complained of an EBS braking fault which occurred intermittently. When the fault occurred then the EBS light would illuminate on the display and the EBS function would revert to conventional braking.

Unspecified DAF ABS fault,
EBS fault,
Unspecified
Toyota
Hilux
2007

Non-starter
Bought at auction. When viewed it was a non-runner, at the actual auction it ran! Numerous warning lights flashing, engine start and stalling, severe engine rattle under brief running conditions and excessive smoke via the exhaust. So where do you start? It has to be the beginning.

Diesel Toyota Engine stalling,
Engine vibrations,
Non-starter,
P0200,
P0340,
P0355,
Diesel
VW
Caddy
2007

Lack of power, poor cold start
If at first you don't succeed...you know the rest. This case study follows post- purchase rectification of a 2007 VW Caddy 1.9 TDI (Engine code BLS). The Caddy was purchased at auction during the summer with the knowledge that the vehicle was not running at its best, but was "running"!

Diesel VW Poor acceleration,
Poor starting,
Diesel
Toyota
Celica
2001

Poor running
The case study below demonstrates how PicoScope fits within the diagnostic jigsaw when resolving seemingly complex issues. The analogy of a jigsaw fits well if we look at the essential pieces required for a successful diagnosis.

Petrol Toyota P0172,
Poor acceleration,
Poor idle,
Petrol
BMW
545 E60
2003

Charging system communication error
Here is one vehicle that has been suffering from repeated breakdowns as a result of what proved to be overvoltage.

Petrol BMW Non-starter,
Poor acceleration,
Petrol
Toyota

Loss of power P1251
The Pico Journey forms a typical yet simple example of how PicoScope sits alongside any scan tool on the road to a successful diagnosis.

Unspecified Toyota MIL on,
P1251,
Power loss,
Unspecified
Maserati
Quattroporte
2010

NVH Cabin Vibration
The trouble with vibrations is that we all interpret them differently (which is why we should measure and not guess), but with this vehicle you could not deny a considerable vibration throughout the vehicle in a very specific engine speed range. Starting at 1450 rpm through to 1700 rpm the vibration was evident, with peak vibration occurring around 1600 rpm.

Petrol Maserati Cabin vibrations,
Engine vibrations,
NVH,
P0200,
Petrol
Ford
Fiesta 1.3 16 V
2001

Misfire
The topic of this case study is not so much "How we managed to diagnose the fault in question" but more about the multiple options at our disposal when it comes to diagnosing component failure.

Petrol Ford Engine misfire,
P0301,
Petrol
VW
Polo 1.2 3-Cyl
2003

Misleading fault codes
When it comes to diagnosis a cool head must be maintained when all around appears to be crumbling. Our relationship with the customer pays dividends during diagnosis where rapport is essential when things appear to go from bad to worse. It is very easy to jump to conclusions when the evidence gathered during diagnosis points to a particular component. It is at this stage we should take stock and step away to ponder before we commit to our diagnosis.

Petrol VW P0106,
P0172,
Petrol
Renault
Clio
2009

Renault Clio Fuel Pressure problem
This 2009 (MK3) Renault Clio 1.5 dCi engine had a complaint just after starting where a strange noise occurred for a few seconds followed by the MIL illuminating and the engine entering recovery mode.

Diesel Renault DF007,
DF885,
MIL on,
Diesel
Honda
CR-V
2007

Honda CR-V with Severe hesitation
During hard acceleration, the vehicle violently surges back and forth. When the accelerator pedal is released, the vehicle resumes normal driving performance. The symptom is evident regardless of engine temperature, and is present whenever the driver attempts hard acceleration (the symptom is permanent).

Diesel Honda Engine surging,
Poor acceleration,
Diesel
BMW
120 M Sport (E87)
2006

Juddering at low speed
Driving at low speed the vehicle appears to judder, accompanied with a yellow warning light illuminated within the instrument panel. The symptom was evident every drive regardless of temperature and road condition, and had been evident for over a week.

Diesel BMW ABS fault,
Diesel
Jaguar
X Type
2006

Jaguar X-type with severe power loss
Engine warning light became illuminated, accompanied with severe lack of power under acceleration after changing gear or when pulling away from rest (evident for approximately 3 weeks).

Diesel Jaguar P0405,
P132A,
Power loss,
Diesel