PID formulas

All live values obd-diag knows, with the key for obd-diag live --pids, unit, conversion according to SAE J1979 (service $01) and value range. The table is generated from PIDS in src/obd_diag/protocol/pids.py when the documentation is built.

tests/verification/test_pid_differential.py compares every formula for every possible byte value with python-OBD. Two deviations are intended and justified against J1979:

• 32 (evap system vapor pressure): 16-bit two’s complement over A and B; python-OBD evaluates A and B separately.

• 44 (commanded air-fuel equivalence ratio): factor exactly 2/65536 instead of the rounded 0.0000305.

The PIDs 68 (intake air temperature per sensor), 6C (throttle actuator), 6D (fuel rail pressure control), 70 (boost pressure) and 85 (AdBlue) are reported as supported by the Mercedes A 180 d, but there are no responses from the car yet: not yet verified on the car. Their structure follows J1979 according to two independent descriptions that agree (OBDb signal list, DashLogic PID list). Each of these PIDs starts with a status byte A that says which values the vehicle provides; if the bit is missing, the value stays empty. A value only appears anyway if the vehicle reports the PID.

Not included are bit fields without a measured value (01, 03, 12, 13, 1C, 1D, 1E, 41, 51, 65, 88, 92, the control status in 70) and PIDs with a status byte whose structure is not unambiguous in free sources or that the test car does not report (among them 69 EGR, 7A–7C particulate filter), as well as 53/54. They will only be added with the standard (J1979-DA) or real responses.

140 values from 87 PIDs, sorted by PID. A, B, C … are the data bytes after 41 <PID>; the range is the full value range of the encoding, not the physically plausible one.

PID	Key	Value	Unit	Formula	Range
04	engine_load	Calculated engine load	%	100*A/255	0 to 100
05	coolant_temp	Coolant temperature	°C	A - 40	-40 to 215
06	stft_bank1	Short-term fuel trim bank 1	%	100*A/128 - 100	-100 to 99.2188
07	ltft_bank1	Long-term fuel trim bank 1	%	100*A/128 - 100	-100 to 99.2188
08	stft_bank2	Short-term fuel trim bank 2	%	100*A/128 - 100	-100 to 99.2188
09	ltft_bank2	Long-term fuel trim bank 2	%	100*A/128 - 100	-100 to 99.2188
0A	fuel_pressure	Fuel pressure (gauge)	kPa	A * 3	0 to 765
0B	intake_pressure	Intake manifold pressure (absolute)	kPa	A	0 to 255
0C	rpm	Engine speed	rpm	(256A + B) / 4	0 to 16383.8
0D	speed	Speed	km/h	A	0 to 255
0E	timing_advance	Timing advance (before TDC, cylinder 1)	°	A / 2 - 64	-64 to 63.5
0F	intake_temp	Intake air temperature	°C	A - 40	-40 to 215
10	maf	Air flow rate (MAF sensor)	g/s	(256A + B) / 100	0 to 655.35
11	throttle	Throttle position	%	100*A/255	0 to 100
14	o2_s1_voltage	Oxygen sensor 1 voltage	V	A / 200	0 to 1.275
14	o2_s1_trim	Oxygen sensor 1 trim	%	100/128 * B - 100; B = FF: sensor not used for fuel trim	-100 to 98.4375
15	o2_s2_voltage	Oxygen sensor 2 voltage	V	A / 200	0 to 1.275
15	o2_s2_trim	Oxygen sensor 2 trim	%	100/128 * B - 100; B = FF: sensor not used for fuel trim	-100 to 98.4375
16	o2_s3_voltage	Oxygen sensor 3 voltage	V	A / 200	0 to 1.275
16	o2_s3_trim	Oxygen sensor 3 trim	%	100/128 * B - 100; B = FF: sensor not used for fuel trim	-100 to 98.4375
17	o2_s4_voltage	Oxygen sensor 4 voltage	V	A / 200	0 to 1.275
17	o2_s4_trim	Oxygen sensor 4 trim	%	100/128 * B - 100; B = FF: sensor not used for fuel trim	-100 to 98.4375
18	o2_s5_voltage	Oxygen sensor 5 voltage	V	A / 200	0 to 1.275
18	o2_s5_trim	Oxygen sensor 5 trim	%	100/128 * B - 100; B = FF: sensor not used for fuel trim	-100 to 98.4375
19	o2_s6_voltage	Oxygen sensor 6 voltage	V	A / 200	0 to 1.275
19	o2_s6_trim	Oxygen sensor 6 trim	%	100/128 * B - 100; B = FF: sensor not used for fuel trim	-100 to 98.4375
1A	o2_s7_voltage	Oxygen sensor 7 voltage	V	A / 200	0 to 1.275
1A	o2_s7_trim	Oxygen sensor 7 trim	%	100/128 * B - 100; B = FF: sensor not used for fuel trim	-100 to 98.4375
1B	o2_s8_voltage	Oxygen sensor 8 voltage	V	A / 200	0 to 1.275
1B	o2_s8_trim	Oxygen sensor 8 trim	%	100/128 * B - 100; B = FF: sensor not used for fuel trim	-100 to 98.4375
1F	run_time	Run time since engine start	s	256*A + B	0 to 65535
21	distance_with_mil	Distance with MIL on	km	256*A + B	0 to 65535
22	fuel_rail_pressure_relative	Fuel rail pressure (relative to manifold)	kPa	(256A + B) * 0.079	0 to 5177.27
23	fuel_rail_pressure	Fuel rail pressure (gauge)	kPa	(256A + B) * 10	0 to 655350
24	o2_s1_lambda	Wide-band sensor 1	Lambda	2/65536 * (256A + B)	0 to 1.99997
24	o2_s1_wide_voltage	Wide-band sensor 1 voltage	V	8/65536 * (256C + D)	0 to 7.99988
25	o2_s2_lambda	Wide-band sensor 2	Lambda	2/65536 * (256A + B)	0 to 1.99997
25	o2_s2_wide_voltage	Wide-band sensor 2 voltage	V	8/65536 * (256C + D)	0 to 7.99988
26	o2_s3_lambda	Wide-band sensor 3	Lambda	2/65536 * (256A + B)	0 to 1.99997
26	o2_s3_wide_voltage	Wide-band sensor 3 voltage	V	8/65536 * (256C + D)	0 to 7.99988
27	o2_s4_lambda	Wide-band sensor 4	Lambda	2/65536 * (256A + B)	0 to 1.99997
27	o2_s4_wide_voltage	Wide-band sensor 4 voltage	V	8/65536 * (256C + D)	0 to 7.99988
28	o2_s5_lambda	Wide-band sensor 5	Lambda	2/65536 * (256A + B)	0 to 1.99997
28	o2_s5_wide_voltage	Wide-band sensor 5 voltage	V	8/65536 * (256C + D)	0 to 7.99988
29	o2_s6_lambda	Wide-band sensor 6	Lambda	2/65536 * (256A + B)	0 to 1.99997
29	o2_s6_wide_voltage	Wide-band sensor 6 voltage	V	8/65536 * (256C + D)	0 to 7.99988
2A	o2_s7_lambda	Wide-band sensor 7	Lambda	2/65536 * (256A + B)	0 to 1.99997
2A	o2_s7_wide_voltage	Wide-band sensor 7 voltage	V	8/65536 * (256C + D)	0 to 7.99988
2B	o2_s8_lambda	Wide-band sensor 8	Lambda	2/65536 * (256A + B)	0 to 1.99997
2B	o2_s8_wide_voltage	Wide-band sensor 8 voltage	V	8/65536 * (256C + D)	0 to 7.99988
2C	commanded_egr	Commanded EGR	%	100*A/255	0 to 100
2D	egr_error	EGR error	%	100*A/128 - 100	-100 to 99.2188
2E	commanded_evap_purge	Commanded evaporative purge	%	100*A/255	0 to 100
2F	fuel_level	Fuel tank level	%	100*A/255	0 to 100
30	warmups_since_clear	Warm-ups since codes cleared		A	0 to 255
31	distance_since_clear	Distance since codes cleared	km	256*A + B	0 to 65535
32	evap_pressure	Evap system vapor pressure	Pa	(256A + B, signed) / 4	-8192 to 8191.75
33	baro_pressure	Barometric pressure (absolute)	kPa	A	0 to 255
34	o2_s1_lambda_current	Wide-band sensor 1 (current)	Lambda	2/65536 * (256A + B)	0 to 1.99997
34	o2_s1_current	Wide-band sensor 1 pump current	mA	(256C + D)/256 - 128	-128 to 127.996
35	o2_s2_lambda_current	Wide-band sensor 2 (current)	Lambda	2/65536 * (256A + B)	0 to 1.99997
35	o2_s2_current	Wide-band sensor 2 pump current	mA	(256C + D)/256 - 128	-128 to 127.996
36	o2_s3_lambda_current	Wide-band sensor 3 (current)	Lambda	2/65536 * (256A + B)	0 to 1.99997
36	o2_s3_current	Wide-band sensor 3 pump current	mA	(256C + D)/256 - 128	-128 to 127.996
37	o2_s4_lambda_current	Wide-band sensor 4 (current)	Lambda	2/65536 * (256A + B)	0 to 1.99997
37	o2_s4_current	Wide-band sensor 4 pump current	mA	(256C + D)/256 - 128	-128 to 127.996
38	o2_s5_lambda_current	Wide-band sensor 5 (current)	Lambda	2/65536 * (256A + B)	0 to 1.99997
38	o2_s5_current	Wide-band sensor 5 pump current	mA	(256C + D)/256 - 128	-128 to 127.996
39	o2_s6_lambda_current	Wide-band sensor 6 (current)	Lambda	2/65536 * (256A + B)	0 to 1.99997
39	o2_s6_current	Wide-band sensor 6 pump current	mA	(256C + D)/256 - 128	-128 to 127.996
3A	o2_s7_lambda_current	Wide-band sensor 7 (current)	Lambda	2/65536 * (256A + B)	0 to 1.99997
3A	o2_s7_current	Wide-band sensor 7 pump current	mA	(256C + D)/256 - 128	-128 to 127.996
3B	o2_s8_lambda_current	Wide-band sensor 8 (current)	Lambda	2/65536 * (256A + B)	0 to 1.99997
3B	o2_s8_current	Wide-band sensor 8 pump current	mA	(256C + D)/256 - 128	-128 to 127.996
3C	catalyst_temp_b1s1	Catalyst temperature bank 1, sensor 1	°C	(256A + B) / 10 - 40	-40 to 6513.5
3D	catalyst_temp_b2s1	Catalyst temperature bank 2, sensor 1	°C	(256A + B) / 10 - 40	-40 to 6513.5
3E	catalyst_temp_b1s2	Catalyst temperature bank 1, sensor 2	°C	(256A + B) / 10 - 40	-40 to 6513.5
3F	catalyst_temp_b2s2	Catalyst temperature bank 2, sensor 2	°C	(256A + B) / 10 - 40	-40 to 6513.5
42	control_voltage	Control module voltage	V	(256A + B) / 1000	0 to 65.535
43	absolute_load	Absolute load value	%	(256A + B) * 100 / 255	0 to 25700
44	commanded_lambda	Commanded air-fuel equivalence ratio	Lambda	2/65536 * (256A + B)	0 to 1.99997
45	relative_throttle	Relative throttle position	%	100*A/255	0 to 100
46	ambient_temp	Ambient air temperature	°C	A - 40	-40 to 215
47	throttle_b	Absolute throttle position B	%	100*A/255	0 to 100
49	accelerator_pedal_d	Accelerator pedal position D	%	100*A/255	0 to 100
4A	accelerator_pedal_e	Accelerator pedal position E	%	100*A/255	0 to 100
4C	commanded_throttle	Commanded throttle actuator	%	100*A/255	0 to 100
4D	time_with_mil	Time run with MIL on	min	256*A + B	0 to 65535
4E	time_since_clear	Time since codes cleared	min	256*A + B	0 to 65535
52	ethanol_percent	Ethanol fuel percentage	%	100*A/255	0 to 100
55	stft_secondary_bank1	Short-term secondary O2 trim bank 1	%	100*A/128 - 100	-100 to 99.2188
55	stft_secondary_bank3	Short-term secondary O2 trim bank 3	%	100*B/128 - 100	-100 to 99.2188
56	ltft_secondary_bank1	Long-term secondary O2 trim bank 1	%	100*A/128 - 100	-100 to 99.2188
56	ltft_secondary_bank3	Long-term secondary O2 trim bank 3	%	100*B/128 - 100	-100 to 99.2188
57	stft_secondary_bank2	Short-term secondary O2 trim bank 2	%	100*A/128 - 100	-100 to 99.2188
57	stft_secondary_bank4	Short-term secondary O2 trim bank 4	%	100*B/128 - 100	-100 to 99.2188
58	ltft_secondary_bank2	Long-term secondary O2 trim bank 2	%	100*A/128 - 100	-100 to 99.2188
58	ltft_secondary_bank4	Long-term secondary O2 trim bank 4	%	100*B/128 - 100	-100 to 99.2188
5A	relative_accelerator_pedal	Relative accelerator pedal position	%	100*A/255	0 to 100
5B	hybrid_battery_level	Hybrid battery state of charge	%	100*A/255	0 to 100
5C	oil_temp	Engine oil temperature	°C	A - 40	-40 to 215
5D	injection_timing	Fuel injection timing	°	(256A + B) / 128 - 210	-210 to 301.992
5E	fuel_rate	Engine fuel rate	L/h	(256A + B) / 20	0 to 3276.75
61	demand_torque	Driver’s demand engine torque	%	A - 125	-125 to 130
62	actual_torque	Actual engine torque	%	A - 125	-125 to 130
63	reference_torque	Engine reference torque	Nm	256*A + B	0 to 65535
64	torque_idle	Engine torque idle	%	A - 125	-125 to 130
64	torque_point1	Engine torque point 1	%	B - 125	-125 to 130
64	torque_point2	Engine torque point 2	%	C - 125	-125 to 130
64	torque_point3	Engine torque point 3	%	D - 125	-125 to 130
64	torque_point4	Engine torque point 4	%	E - 125	-125 to 130
66	maf_a	Mass air flow sensor A	g/s	(256B + C) / 32; only if bit 0 of A is set	0 to 2047.97
66	maf_b	Mass air flow sensor B	g/s	(256D + E) / 32; only if bit 1 of A is set	0 to 2047.97
67	coolant_temp_1	Coolant temperature sensor 1	°C	B - 40; only if bit 0 of A is set	-40 to 215
67	coolant_temp_2	Coolant temperature sensor 2	°C	C - 40; only if bit 1 of A is set	-40 to 215
68	intake_temp_b1s1	Intake air temperature bank 1, sensor 1	°C	B - 40; only if bit 0 of A is set	-40 to 215
68	intake_temp_b1s2	Intake air temperature bank 1, sensor 2	°C	C - 40; only if bit 1 of A is set	-40 to 215
68	intake_temp_b1s3	Intake air temperature bank 1, sensor 3	°C	D - 40; only if bit 2 of A is set	-40 to 215
68	intake_temp_b2s1	Intake air temperature bank 2, sensor 1	°C	E - 40; only if bit 3 of A is set	-40 to 215
68	intake_temp_b2s2	Intake air temperature bank 2, sensor 2	°C	F - 40; only if bit 4 of A is set	-40 to 215
68	intake_temp_b2s3	Intake air temperature bank 2, sensor 3	°C	G - 40; only if bit 5 of A is set	-40 to 215
6C	commanded_throttle_a	Commanded throttle actuator A	%	100*B/255; only if bit 0 of A is set	0 to 100
6C	relative_throttle_a	Relative throttle position A	%	100*C/255; only if bit 1 of A is set	0 to 100
6C	commanded_throttle_b	Commanded throttle actuator B	%	100*D/255; only if bit 2 of A is set	0 to 100
6C	relative_throttle_b	Relative throttle position B	%	100*E/255; only if bit 3 of A is set	0 to 100
6D	commanded_fuel_rail_pressure_a	Commanded fuel rail pressure A	kPa	(256B + C) * 10; only if bit 0 of A is set	0 to 655350
6D	fuel_rail_pressure_a	Fuel rail pressure A	kPa	(256D + E) * 10; only if bit 1 of A is set	0 to 655350
6D	fuel_rail_temp_a	Fuel rail temperature A	°C	F - 40; only if bit 2 of A is set	-40 to 215
6D	commanded_fuel_rail_pressure_b	Commanded fuel rail pressure B	kPa	(256G + H) * 10; only if bit 3 of A is set	0 to 655350
6D	fuel_rail_pressure_b	Fuel rail pressure B	kPa	(256I + J) * 10; only if bit 4 of A is set	0 to 655350
6D	fuel_rail_temp_b	Fuel rail temperature B	°C	K - 40; only if bit 5 of A is set	-40 to 215
70	commanded_boost_a	Commanded boost pressure A	kPa	(256B + C) / 32; only if bit 0 of A is set	0 to 2047.97
70	boost_a	Boost pressure A	kPa	(256D + E) / 32; only if bit 1 of A is set	0 to 2047.97
70	commanded_boost_b	Commanded boost pressure B	kPa	(256F + G) / 32; only if bit 3 of A is set	0 to 2047.97
70	boost_b	Boost pressure B	kPa	(256H + I) / 32; only if bit 4 of A is set	0 to 2047.97
85	reagent_consumption	Reagent consumption (average)	L/h	(256B + C) / 200; only if bit 0 of A is set	0 to 327.675
85	reagent_demand	Reagent demand (average)	L/h	(256D + E) / 200; only if bit 1 of A is set	0 to 327.675
85	reagent_level	Reagent tank level	%	100*F/255; only if bit 2 of A is set	0 to 100
85	nox_warning_time	Run time with NOx warning	s	(2^24 G + 2^16 H + 2^8 I + J); only if bit 3 of A is set	0 to 4.29497e+09
A6	odometer	Odometer	km	(2^24 A + 2^16 B + 2^8 C + D) / 10	0 to 4.29497e+08