False P1299 Engine Over Temp Condition
09-03-2012, 12:55 PM
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False P1299 Engine Over Temp Condition
I have had an interesting ongoing problem with my '97 F-150 with a 4.6 L V8, and am looking for some ideas on how to fix it....
Several times, ONLY when towing a trailer, and EVERY TIME I tow a trailer, within 15 to 60 minutes of normal highway driving I get a "Check Engine" light coming on, soon followed by transition to "limp-home" mode (low power output from the engine). No other indications of problems, in particular the temperature stays normal (180-190 deg F, according to a mercury bulb aftermarket temp gauge installed in my truck). When I shut the engine down and restart, the "limp-home" mode disappears, and if I continue towing the trailer, the same sequence of events will eventually recur. Once I remove the trailer and resume normal no-trailer driving, the Check Engine light stays on, but after a couple of days without the trailer (during which "limp-home" never activates....), the light goes out. The truck runs fine without a trailer. The trailer is not a heavy trailer (~2000 lb max). Luckily, I rarely have to pull it, and then only for short distances.... But I need to do a long trip soon with the trailer, so I must fix this problem.
The last time this happened, I had a maintenance code reader with me, and here is what it gave me:
P1299 Mod $10 Society of Automotive Engineers - Engine Over Temperature Condition
TROUB CODE P1299
ENG SPEED (RPM) 1660
CALC LOAD (%) 91.4
COOLANT (DEG F) 189
ST FTRM1 (%) 4.7
LT FTRM1 (%) 3.1
ST FTRM2 (%) 4.7
LT FTRM2 (%) 3.1
VEH SPEED (MPH) 57
FUEL SYS 1 OPEN1
FUEL SYS 2 N/A
On that day, at idle, the real-time readout from the code reader was as follows:
MIL STATUS ON
ABSLT TPS (%) 18.4
ENG SPEED (RPM) 704
CALC LOAD (%) 38.0
MAP (LB/M) 0.81
COOLANT (DEG F) 185
IAT (DEG F) 111
IGN ADV (DEG) 13.5
ST FTRM1 (%) 4.7
LT FTRM1 (%) 9.4
ST FTRM2 (%) 4.7
LT FTRM2 (%) 7.0
VEH SPEED (MPH) 0
FUEL SYS 1 OPEN1
FUEL SYS 2 N/A
O2S11 (V) 0.755
ST FTRM11 (%) 4.7
O2S12 (V) 0.785
O2S21 (V) 0.810
ST FTRM21 (%) 4.7
O2S22 (V) 0.760
OBD2 STAT CA
In particular, note that the fault is reported as "Engine Over Temperature Condition". But I am sure the engine is below 200 deg. This temperature is confirmed by both the the computer readings and the mercury bulb aftermarket temp gauge I have installed in my truck.
I don't know whether the other readings from the code reader are normal or not, can anyone comment on if there is a problem the above readings might indicate?
My mechanic says my engine computer (ECM?) is "gone haywire" and I need a new one. I am not getting the feeling that he is sure about this, it feels like he just wants to try it. I would hate to spend the money on a new computer if it's something else....
One more thing that might mean something: The reason why I have the aftermarket temperature gauge is that at one point the stock temp gauge started giving me spurious (and known incorrect) sudden max-temp spike readings (which of course are physically impossible). I figured this was likely due to a short in the dash OR in the wire harness. I may have pinched a wire during some work under the hood, and caused an intermittent short. So, I just unhooked the stock wire, removed the stock sensor, and replaced it with the aftermarket sensor and gauge. The issue with the stock temp gauge AND the situation when towing the trailer showed up about the same time. Could a different pinched wire/intermittent short be causing the incorrect P1299? But if so, why would the temp reading from the computer show a benign reading like 189 deg F?
Any ideas would be appreciated....
Several times, ONLY when towing a trailer, and EVERY TIME I tow a trailer, within 15 to 60 minutes of normal highway driving I get a "Check Engine" light coming on, soon followed by transition to "limp-home" mode (low power output from the engine). No other indications of problems, in particular the temperature stays normal (180-190 deg F, according to a mercury bulb aftermarket temp gauge installed in my truck). When I shut the engine down and restart, the "limp-home" mode disappears, and if I continue towing the trailer, the same sequence of events will eventually recur. Once I remove the trailer and resume normal no-trailer driving, the Check Engine light stays on, but after a couple of days without the trailer (during which "limp-home" never activates....), the light goes out. The truck runs fine without a trailer. The trailer is not a heavy trailer (~2000 lb max). Luckily, I rarely have to pull it, and then only for short distances.... But I need to do a long trip soon with the trailer, so I must fix this problem.
The last time this happened, I had a maintenance code reader with me, and here is what it gave me:
P1299 Mod $10 Society of Automotive Engineers - Engine Over Temperature Condition
TROUB CODE P1299
ENG SPEED (RPM) 1660
CALC LOAD (%) 91.4
COOLANT (DEG F) 189
ST FTRM1 (%) 4.7
LT FTRM1 (%) 3.1
ST FTRM2 (%) 4.7
LT FTRM2 (%) 3.1
VEH SPEED (MPH) 57
FUEL SYS 1 OPEN1
FUEL SYS 2 N/A
On that day, at idle, the real-time readout from the code reader was as follows:
MIL STATUS ON
ABSLT TPS (%) 18.4
ENG SPEED (RPM) 704
CALC LOAD (%) 38.0
MAP (LB/M) 0.81
COOLANT (DEG F) 185
IAT (DEG F) 111
IGN ADV (DEG) 13.5
ST FTRM1 (%) 4.7
LT FTRM1 (%) 9.4
ST FTRM2 (%) 4.7
LT FTRM2 (%) 7.0
VEH SPEED (MPH) 0
FUEL SYS 1 OPEN1
FUEL SYS 2 N/A
O2S11 (V) 0.755
ST FTRM11 (%) 4.7
O2S12 (V) 0.785
O2S21 (V) 0.810
ST FTRM21 (%) 4.7
O2S22 (V) 0.760
OBD2 STAT CA
In particular, note that the fault is reported as "Engine Over Temperature Condition". But I am sure the engine is below 200 deg. This temperature is confirmed by both the the computer readings and the mercury bulb aftermarket temp gauge I have installed in my truck.
I don't know whether the other readings from the code reader are normal or not, can anyone comment on if there is a problem the above readings might indicate?
My mechanic says my engine computer (ECM?) is "gone haywire" and I need a new one. I am not getting the feeling that he is sure about this, it feels like he just wants to try it. I would hate to spend the money on a new computer if it's something else....
One more thing that might mean something: The reason why I have the aftermarket temperature gauge is that at one point the stock temp gauge started giving me spurious (and known incorrect) sudden max-temp spike readings (which of course are physically impossible). I figured this was likely due to a short in the dash OR in the wire harness. I may have pinched a wire during some work under the hood, and caused an intermittent short. So, I just unhooked the stock wire, removed the stock sensor, and replaced it with the aftermarket sensor and gauge. The issue with the stock temp gauge AND the situation when towing the trailer showed up about the same time. Could a different pinched wire/intermittent short be causing the incorrect P1299? But if so, why would the temp reading from the computer show a benign reading like 189 deg F?
Any ideas would be appreciated....
