Dan Marinucci Almost nothing escapes detection by current engine
Contents
1. service manual two sets of conditions can set this code The first is when the start signal is on and engine speed remains below 500 rpm an abnor mally long time at a given coolant temperature So suppose the ECM reads bat tery voltage at terminal STA It thinks the driver is trying to start the engine The moment the com puter sees the start signal it com pares rom to coolant temperature the ECM expects the engine to ex ceed 500 rom within so many sec onds at a particular temperature It stores P1604 if it senses a start sig nal and the engine doesn t exceed 500 rom within the proper time at a specified coolant temperature The colder the coolant temperature the longer the starting time the ECM allows To give you some idea of the time frame involved here referred to a Toyota chart comparing start time to engine coolant At a coolant tem perature of approximately 28 F the chart indicated the engine should reach 500 rpm in 2 seconds T here fore the basic problems or com bination of them that reduce cranking speed are going to be the likely causes of a P1604 code In the case of M att s customer for in stance it was a combination of bru tal cold an unused vehicle and a weak battery The second situation for a starta bility code is when the engine starts up but then either stumbles badly or stalls Suppose for instance that the engine exceeds 500 rpm and starts up But then rpm drops to2. 200 rpm or less within about 2 sec onds after start up In that case the computer stores P1604 To put it another way the ECM is watching for engine speed to drop too much too abruptly right after start up In this scenario then your focus is not an abnormally long crank time In stead it s a start amp stall or start amp stumble diagnosis Fix Fundamentals First If a P1604 code occurs by all means record the freeze frame data and study it for clues especially coolant temperature and battery voltage Sometimes you may need to do what you ve done on other diag noses Recreate the same conditions as those cited on the freeze frame If the startability code is the only one stored diagnose and repair the fundamentals Then clear the code and the vehicle ought to be fine Watch out for a code or codes that appear along with P1604 Basically the cause s of the other code or codes set the stage created the con ditions that triggered the startabili ty code Understandably the service manual emphasizes that you should always diagnose and correct the caus es of the other codes first Ignoring them is nearly sure to cause a recur ring P1604 So all things considered this new code Is likely to route us right back to testing the basics Talk about fundamentals Meantime up in the northern tier Matt hopes it ll be warm enough to swim by the time they unload the fireworks Don t you think this gentleman n
3. Dan Marinucci dmarinucci motor com Almost nothing escapes detection by current engine management computers A seemingly innocuous startability trouble code on some late model Toyota vehicles may warn of future problems ndependence Day comes in July and many people think the Fourth just isn t complete without a fabulous fireworks display Of course fireworks occur in automo tive repair shops too Spilled fuel may catch fire or a live circuit may ground out somewhere But the worst kind may be those emotional fireworks fueled by the frustration of an unsolved problem This month s column concerns one such incident when an odd trouble code appeared on a Toyota H ere s what we learned M y colleague M att has a shop up in the northern tier of New York State He s been working hard to gather all the routine man ufacturer mandated maintenance work pos sible Obviously a consistent log of mainte Se FDROMETEON Cee En EVE HARAGEI CLEAR A LEGH TELL iy a Ep OG TLLES WATER ifn ETE 5 iSCHARGED nance appointments Is very beneficial today The owner of a 2011 Toyota Yaris is among the maintenance customers M att s shop at tracted Last winter this Yaris happened to sit un used for a week and a half The owner s wife had become sick and he stayed home to take care of her But after 10 days he finally had to run errands again Fortunately the car s battery had some life left in it But u
4. eeds a heated pool Just don t tell him suggested that expenditure DENSO 1 2 PG ISLAND 4C July 2013 MOTOR 19
5. nder standably cranking speed was very slow Luckily for him the engine finally fired up after several tries It soewed some black ex haust smoke and Initially ran as if the choke was stuck on he noted We can guess this fellow s age by the fact that he re membered the symptoms of a stuck choke Prior to this incident the car had been continued on page 18 GROUP 24F Uo 562 AMPS z gq S 125 MINUTES RECUPERER RECTCLE 030205 ust ay TOYO ROTOR HEC ENIT kanes mal apart none KY 10 14 JHA COMI PATO Gey reed WA i i a A DANGER POISON russ ieee TEL ap 7 c pP Siw l TTH RATER han j SAFU ACID GET HEDEN HELP AAST lio oa toe nE vint qp CAFS NOHT Ai LE EE A oF THe ee oo A weak battery and the resulting slow cranking speed can cause DIC P1604 to set on some late model Toyota vehicles This code is a relatively new one on Toyota engine control systems 16 MOTOR July 2013 Foreign Service running well According to M att s records the car had 17 000 miles on it and he had done all the recom mended maintenance No trouble codes were present or pending dur ing the car s last service H owever the Check Engine light came on af ter the fellow finally restarted the car on that brutally cold morning Then much to Matt s dismay he took it to the Toyota dealer first for an evaluation Later the man had second thoughts about the dealer s response and drove it to M att s shop I
6. nterestingly no one at the dealership had cleared the code DENSO 1 2 PG ISLAND 4C 18 MOTOR July 2013 According to the Yaris owner the dealer s service personnel said the Check Engine light and trouble code DTC P1604 were typical re actions to the hard starting condi tion Their conclusion was that the situation was normal especially since no other codes were present or pending One of Matt s techs scanned the Yaris verifying that the P1604 was the only code stored Unfortunately the lad jumped the gun and cleared the DTC without recording its freeze frame data So the basic history of the event was lost H owever M att has followed up with the Yaris owner since then The car has been running like a top no additional trouble codes or symptoms have occurred Start Now or Else Okay let s look more closely at DTC P1604 This is arelatively new code on Toyota vehicles it s been in service for only a few model years Because the service manual dubs it a startability code we ll begin with the STA start signal If you turn the ignition switch to the Start position on a typical Toyota prod uct the ignition switch applies bat tery voltage to the ECM s STA ter minal Whenever the ECM mea sures battery voltage at terminal STA it knows the driver is trying to crank the engine The start signal STA coolant temperature and engine speed could combine to trigger DTC P1604 According to the
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